Spatial wavefront analysis and 3D measurement

ABSTRACT

A method of wavefront ( 100 ) analysis including applying a transform to the wavefront, applying a plurality of different phase changes ( 110, 112, 114 ) to the transformed wavefront ( 108 ), obtaining a plurality of intensity maps ( 130, 132, 134 ) wherein the plurality of different phase changes are applied to region of the transformed wavefront, corresponding to a shape of the light source.

REFERENCE TO CO-PENDING APPLICATIONS

Applicant hereby claims priority of U.S. Provisional Patent ApplicationSer. No. 60/351,753, filed on Jan. 24, 2002, entitled “Improved SpatialWavefront Analysis and Measurement” and U.S. Provisional PatentApplication Ser. No. 60/406,593, filed on Aug. 27, 2002, entitled “BestMethods for Spatial Wavefront Analysis and 3D Measurement”.

FIELD OF THE INVENTION

The present invention relates to the field of spatial wavefrontanalysis.

BACKGROUND OF THE INVENTION

The following patents and publications are believed to represent thecurrent state of the art:

U.S. patents:

U.S. Pat. Nos. 5,969,855; 5,969,853; 5,936,253; 5,870,191; 5,814,815;5,777,736; 5,751,475; 5,619,372; 5,600,440; 5,471,303; 5,446,540;5,235,587; 5,159,474; 4,653,921; 4,407,569 and 4,190,366.

Other Patents:

JP 9230947 (Abstract); JP 9179029 (Abstract); JP 8094936 (Abstract); JP7261089 (Abstract); JP 7225341 (Abstract); JP 6186504 (Abstract); EP0555099; GB 2315700

Other Publications:

Phillion, D. W., “General methods for generating phase-shiftinginterferometry algorithms”—Applied Optics, Vol. 36, 8098 (1997);

Pluta, M., “Stray-light problem in phase contrast microscopy or towardhighly sensitive phase contrast devices: a review”—Optical Engineering,Vol. 32, 3199 (1993);

Noda, T. and Kawata, S., “Separation of phase and absorption images inphase-contrast microscopy”—Journal of the Optical Society of America A,Vol. 9, 924 (1992);

Creath, K., “Phase measurement interferometry techniques”—Progress inOptics XXVI, 348 (1988);

Greivenkamp, J. E., “Generalized data reduction for heterodyneinterferometry”—Optical Engineering, Vol. 23, 350 (1984);

Morgan, C. J., “Least-squares estimation in phase-measurementinterferometry”—Optics Letters, Vol. 7, 368 (1982);

Golden, L. J., “Zernike test. 1: Analytical aspects”—Applied Optics,Vol. 16, 205 (1977);

Bruning, J. H., et al. “Digital wavefront measuring interferometer fortesting optical surfaces and lenses”—Applied Optics, Vol. 13, 2693(1974); and

Gerchberg, R. W. and Saxton, W. O., Optik 35, 237: (1972).

SUMMARY OF THE INVENTION

The current invention provides elaborated, improved and enhancedmethodologies and systems for wavefront analysis and 3D measurements.These include innovative methods, improved algorithms and hardware,additional implementations, various additional applications andcombinations with other methods and inventions.

There is thus provided in accordance with a preferred embodiment of thepresent invention a method of wavefront analysis including utilizing alight source to illuminate an object and to obtain a wavefront having anamplitude and a phase, obtaining a plurality of differently phasechanged transformed wavefronts corresponding to the wavefront beinganalyzed, including applying a transform to the wavefront being analyzedthereby to obtain a transformed wavefront and applying a plurality ofdifferent phase changes to the transformed wavefront, thereby to obtaina plurality of differently phase changed transformed wavefronts,obtaining a plurality of intensity maps of the plurality of phasechanged transformed wavefronts by phase manipulation and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, wherein the plurality ofdifferent phase changes are applied to a region of the transformedwavefront, corresponding to a shape of the light source.

Preferably, the light source includes an elongate light source.

There is also provided in accordance with another preferred embodimentof the present invention a method of wavefront analysis includingutilizing a light source to illuminate an object and to obtain awavefront having an amplitude and a phase, obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to thewavefront being analyzed, including applying a transform to thewavefront being analyzed thereby to obtain a transformed wavefront andapplying a plurality of different phase changes to the transformedwavefront, thereby to obtain a plurality of differently phase changedtransformed wavefronts, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts by phase manipulationand employing the plurality of intensity maps to obtain an outputindicating the amplitude and phase of the wavefront being analyzed,wherein the plurality of different phase changes are applied to regionsof the transformed wavefront, corresponding to a grating.

There is further provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, and wherein obtaining aplurality of differently phase changed transformed wavefronts includesapplying a transform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein thetransformed wavefront includes a plurality of different polarizationcomponents and the plurality of different phase changes are effected byusing a birefringent phase changer to apply different phase changes tothe plurality of different polarization components of the transformedwavefront.

There is also provided in accordance with still another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining two differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed which has an amplitude and aphase, obtaining two intensity maps of the two phase changed transformedwavefronts, employing interference between the two intensity maps togenerate a third intensity map and employing the two intensity maps andthe third intensity map to obtain an output indicating the amplitude andphase of the wavefront being analyzed.

There is further provided in accordance with another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, and wherein obtaining aplurality of differently phase changed transformed wavefronts includesapplying a transform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein theplurality of different phase changes includes spatial phase changes, theplurality of different spatial phase changes are effected by applying aspatially uniform, time-varying spatial phase change to part of thetransformed wavefront, the transform applied to the wavefront beinganalyzed is a Fourier transform, the plurality of different spatialphase changes includes at least three different phase changes, theplurality of intensity maps includes at least three intensity maps andthe employing step includes expressing the wavefront being analyzed as afirst complex function which has an amplitude and phase identical to theamplitude and phase of the wavefront being analyzed, expressing theplurality of intensity maps as a function of the first complex functionand of a spatial function governing the spatially uniform, time-varyingspatial phase change, defining a second complex function, having anabsolute value and a phase, as a convolution of the first complexfunction and of a Fourier transform of the spatial function governingthe spatially uniform, time-varying spatial phase change, expressingeach of the plurality of intensity maps as a third function of theamplitude of the wavefront being analyzed, a square of the absolutevalue of the second complex function, a difference between the phase ofthe wavefront being analyzed and the phase of the second complexfunction and a known phase delay produced by one of the at least threedifferent phase changes which each correspond to one of the at leastthree intensity maps, solving the third function to obtain the amplitudeof the wavefront being analyzed, the absolute value of the secondcomplex function and the difference between the phase of the wavefrontbeing analyzed and the phase of the second complex function, solving thesecond complex function to obtain the phase of the second complexfunction and obtaining the phase of the wavefront being analyzed byadding tile phase of the second complex function to the differencebetween the phase of the wavefront being analyzed and the phase of thesecond complex function, the square of the absolute value of the secondcomplex function is obtained by approximating a square of the absolutevalue to a polynomial of a given degree and the employing step includescomputing a confidence level map characterizing confidence in each of aplurality of portions of the phase of the wavefront being analyzed, bycomparing the square of the absolute value of the second complexfunction to the polynomial of a given degree, the confidence level mapincluding a plurality of confidence levels respectively corresponding toa plurality of portions within the intensity maps.

Preferably, the applying a plurality of different phase changes isperformed at least twice using at least two pluralities of differentphase changes and the step of employing is performed at least twiceusing the at least two pluralities of different phase changes, therebyto obtain at least two values for the phase of the wavefront beinganalyzed, and the method also includes using the at least two confidencelevel maps resulting from performing the confidence level mapcomputation step at least twice, to combine the at least two values forthe phase of the wavefront being analyzed into a single value.

Preferably, the step of combining includes selecting a “best” value fromamong the at least two values for the phase of the wavefront beinganalyzed. Additionally, the step of combining includes computing aweighted average of the at least two values for the phase of thewavefront being analyzed, using the confidence levels included in the atleast two confidence level maps as weights for the at least two valuesrespectively.

Alternatively, the method also includes computing the confidence in eachof a plurality of portions of the phase, using, for at least oneportion, a phase value which is different from that measured for the atleast one portion and, if the confidence computed for an individualportion using the different phase value exceeds the confidence computedusing the measured phase value, replacing the measured phase value forthe individual portion with the different phase value.

Preferably, the wavefront being analyzed includes a plurality ofwavefront components having different wavelengths, and the plurality ofdifferently phase changed transformed wavefronts are obtained byapplying a phase change to the plurality of different wavelengthcomponents of the wavefront being analyzed, and the wavefront beinganalyzed includes a plurality of different wavelength components and theplurality of differently phase changed transformed wavefronts areobtained by applying a phase change to the plurality of differentwavelength components of the wavefront being analyzed. Alternatively,the step of applying a plurality of different phase changes is performedfor each of the plurality of wavefront components, and the step ofemploying is performed for each of the plurality of wavefrontcomponents, thereby to obtain a corresponding plurality of values forthe phase of the wavefront being analyzed, and the method also includesusing the at least-confidence level maps resulting from performing theconfidence level map computation step a plurality of times, to combinethe plurality of values for the phase of the wavefront being analyzedinto a single value.

There is also provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining, a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas an amplitude and a phase, obtaining a plurality of intensity maps ofthe plurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, wherein the step of employingalso includes normalizing each of the plurality of intensity maps toobtain a plurality of intensity maps having the same sum of intensityvalues.

Preferably, the plurality of differently phase changed transformedwavefronts are obtained so as to maximize contrast between the pluralityof intensity maps and to minimize effects of noise on the phase of thewavefront being analyzed.

There is further provided in accordance with still another preferredembodiment of the present invention a method of phase change analysisincluding obtaining a phase change analysis wavefront which has anamplitude and a phase, applying a transform to the phase change analysiswavefront thereby to obtain a transformed wavefront, applying at leastone phase change to the transformed wavefront, thereby to obtain atleast one phase changed transformed wavefront, obtaining at least oneintensity map of the at least one phase changed transformed wavefrontand employing the at least one intensity map to obtain an outputindication of the at least one phase change applied to the transformedphase change analysis wavefront.

In accordance with another preferred embodiment, the applying at leastone phase change to the transformed wavefront includes applying a phasedelay value to an area within the transformed wavefront and the step ofemploying the at least one intensity map includes obtaining an outputindication delimiting the area.

Preferably, the obtaining a phase change analysis wavefront includesreflecting light off a known object and using the light reflected offthe known object as the phase change analysis wavefront. Alternatively,the obtaining a phase change analysis wavefront includes transmittinglight through a known object and using the transmitted light exiting theknown object as the phase change analysis wavefront.

Alternatively, the employing the at least one intensity map includesderiving at least one contrast map from the at least one intensity mapand employing the at least one contrast map to obtain an outputindication of the at least one phase change applied to the transformedphase change analysis wavefront.

There is also provided in accordance with another preferred embodimentof the present invention a method of wavefront analysis includingobtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity naps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, the method also includingperforming the obtaining steps and the employing step wherein thewavefront being analyzed includes a wavefront originating from a knownobject having known amplitude and phase values, computing amplitude andphase calibration values by comparing the output of the employing stepperformed on the known object to the known amplitude and phase valuesand when performing the obtaining and employing steps on an unknownobject, using the amplitude and phase calibration values to correct theoutput for the unknown object generated in the employing step.

Preferably, the wavefront originating from the known object includes awavefront reflected from the known object. Alternatively, the wavefrontoriginating from the known object includes a wavefront transmittedthrough the known object.

In accordance with a preferred embodiment, the known object includes aflat mirror. Alternatively, the known object includes a window.

There is further provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, and also including using aniris to block off a portion of a wavefront, thereby to generate thewavefront being analyzed, and wherein the plurality of intensity mapsare obtained using a camera having an imaging area which is larger thanthe image of the iris on the imaging area.

There is also provided in accordance with still another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, wherein obtaining a pluralityof differently phase changed transformed wavefronts includes applying atransform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, the plurality ofdifferent phase changes includes spatial phase changes, and theplurality of different spatial phase changes are effected by applying aspatially uniform, time-varying spatial phase change to part of thetransformed wavefront and the transform applied to the wavefront beinganalyzed is a Fourier transform, the step of employing includesexpressing the wavefront being analyzed as a first complex functionwhich has an amplitude and phase identical to the amplitude and phase ofthe wavefront being analyzed, expressing the plurality of intensity mapsas a function of the first complex function and of a spatial functiongoverning the spatially uniform, time-varying spatial phase change,defining a second complex function, having an absolute value and aphase, as a convolution of the first complex function and of a Fouriertransform of the spatial function governing the spatially uniform,time-varying spatial phase change, expressing each of the plurality ofintensity maps as a third function of the amplitude of the wavefrontbeing analyzed, the absolute value of the second complex function, adifference between the phase of the wavefront being analyzed and thephase of the second complex function and a known phase delay produced byone of the different phase changes which each correspond to one of theintensity maps, solving the third function to obtain the amplitude ofthe wavefront being analyzed, the absolute value of the second complexfunction and the difference between the phase of the wavefront beinganalyzed and the phase of the second complex function, solving thesecond complex function to obtain the phase of the second complexfunction and obtaining the phase of the wavefront being analyzed byadding the phase of the second complex function to the differencebetween the phase of the wavefront being analyzed and the phase of thesecond complex function, wherein the step of obtaining an outputincludes employing the plurality of intensity maps and the square of theabsolute value of the second complex function to obtain the output.

There is further provided in accordance with another preferredembodiment of the present invention a method for analyzing a wavefronthaving an amplitude and a phase, the method including, using an iris toblock off a portion of a wavefront, thereby to generate a wavefrontbeing analyzed, Fourier-transforming the wavefront being analyzed andeffecting a spatial phase change on a portion of the transformedwavefront, thereby to generate at least one partially phase changedtransformed wavefront, including a known phase changed wavefront portionand a phase unchanged wavefront portion, obtaining at least oneintensity map of the at least one partially phase changed transformedwavefront, the map representing interference between the phase changedportion and the phase unchanged portion, wherein the map is obtainedusing a camera having an imaging area which is larger than the image ofthe iris on the imaging area, thereby to define inside and outside mapportions representing intensity of light impinging on the imaging areaportion inside and outside the iris image respectively and employing theat least one intensity map to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, including expressing thewavefront being analyzed as a first complex function which has anamplitude and phase identical to the amplitude and phase of thewavefront being analyzed, expressing the intensity map as a function ofthe first complex function and of a spatial function and defining asecond complex function, having an absolute value and a phase, as aconvolution of the first complex function and of a Fourier transform ofthe spatial function, wherein the absolute value of the second complexfunction is obtained by approximating the absolute value to a polynomialof a given degree, and the square of the absolute value of the secondcomplex function is derived from the portion of the imaging area whichis external to the image of the iris on the imaging area, assuming thatthe phase of the second complex function is constant over, the imagingarea and computing the amplitude and phase of the wavefront beinganalyzed by assuming the inside map portion represents interferencebetween the wavefront being analyzed and a wavefront having the absolutevalue of the second complex function as an amplitude and having a phasewhich is constant over the imaging area.

In accordance with another preferred embodiment of the present inventionthe obtaining a plurality of differently phase changed transformedwavefronts includes applying a transform to the wavefront being analyzedthereby to obtain a transformed wavefront and applying a plurality ofdifferent phase changes to the transformed wavefront, thereby to obtaina plurality of differently phase changed transformed wavefronts, theplurality of different phase changes includes spatial phase changes, theplurality of different spatial phase changes are effected by applying aspatially uniform, time-varying spatial phase change to part of thetransformed wavefront, the transform applied to the wavefront beinganalyzed is a Fourier transform, the plurality of different spatialphase changes includes at least three different phase changes, theplurality of intensity maps includes at least three intensity maps andthe employing includes expressing the wavefront being analyzed as afirst complex function which has an amplitude and phase identical to theamplitude and phase of the wavefront being analyzed, expressing theplurality of intensity maps as a function of the first complex functionand of a spatial function governing the spatially uniform, time-varyingspatial phase change, defining a second complex function, having anabsolute value and a phase, as a convolution of the first complexfunction and of a Fourier transform of the spatial function governingthe spatially uniform, time-varying spatial phase change, expressingeach of the plurality of intensity maps as a third function of theamplitude of the wavefront being analyzed, the absolute value of thesecond complex function, a difference between the phase of the wavefrontbeing analyzed and the phase of the second complex function and a knownphase delay produced by one of the at least three different phasechanges which each correspond to one of the at least three intensitymaps, solving the third function to obtain the amplitude of thewavefront being analyzed, the absolute value of the second complexfunction and the difference between the phase of the wavefront beinganalyzed and the phase of the second complex function, solving thesecond complex function to obtain the phase of the second complexfunction and obtaining the phase of the wavefront being analyzed byadding the phase of the second complex function to the differencebetween the phase of the wavefront being analyzed and the phase of thesecond complex function, and wherein the square of the absolute value ofthe second complex function is derived from the portion of the imagingarea which is external to the image of the iris on the imaging area.

There is also provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase-changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, wherein obtaining a pluralityof differently phase changed transformed wavefronts includes applying atransform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein theplurality of different phase changes includes spatial phase changes, theplurality of different spatial phase changes are effected by applying aspatial phase change to part of the transformed wavefront, and the stepof applying a plurality of different phase changes includes duplicatingthe transformed wavefront into several wavefronts and wherein the stepof applying a plurality of different phase changes includes applying adifferent spatial phase change to each of the several wavefronts.

Preferably, the step of duplicating includes splitting the beam formingthe transformed wavefront.

There is further provided in accordance with still another preferredembodiment of the present invention a method of providing simultaneoussurface and layer thickness measurements of a multilayer objectincluding illuminating the multilayer object with broadbandillumination, analyzing illumination emerging from the multilayer objectto provide a spectral analysis output and utilizing the spectralanalysis output, simultaneously to provide surface and layer thicknessinformation regarding the multilayer object.

In accordance with another preferred embodiment the analyzinginformation includes performing at least one of phase manipulation andamplitude manipulation on illumination reflected from the multilayerobject to obtain a plurality of reflected illumination intensity maps atdifferent wavelengths and employing the plurality of intensity maps toobtain an output representing the surface and layer thickness of atleast one layer of the multilayer object.

Preferably, the method also includes obtaining a reflected wavefronthaving an amplitude and a phase, by reflecting radiation from a surface;and analyzing the reflected wavefront by obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to thereflected wavefront, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality: of intensity maps to obtain an output indicating theamplitude and phase of the reflected wavefront.

Additionally, the radiation reflected from the surface has at least twonarrow bands, each centered about a different wavelength, providing atleast two wavelength components in the surface mapping wavefront and atleast two indications of the phase of the surface mapping wavefront,thereby enabling an enhanced mapping of the surface to be obtained byavoiding an ambiguity in the mapping which exceeds the larger of thedifferent wavelengths about which the two narrow bands are centered.

In accordance with yet another preferred embodiment, the wavefront beinganalyzed includes a plurality of different wavelength components and theplurality of differently phase changed transformed wavefronts areobtained by applying a phase change to the plurality of differentwavelength components of the wavefront being analyzed. Preferably, theplurality of intensity maps includes at least four intensity maps andemploying the plurality of intensity maps to obtain an output indicatingthe amplitude and phase of the wavefront being analyzed includesemploying a plurality of combinations, each of at least three of theplurality of intensity maps, to provide a plurality of indications ofthe amplitude and phase of the wavefront being analyzed. Alternatively,the wavefront being analyzed includes at least two wavelengthcomponents, the obtaining a plurality of intensity maps also includesdividing the phase changed transformed wavefronts according to the atleast two wavelength components in order to obtain at least twowavelength components of the phase changed transformed wavefronts and inorder to obtain at least two sets of intensity maps, each setcorresponding to a different one of the at least two wavelengthcomponents of the phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed includes obtaining an outputindicative of the phase of the wavefront being analyzed from each of theat least two sets of intensity maps and combining the outputs to providean enhanced indication of phase of the wavefront being analyzed, inwhich enhanced indication, there is no ambiguity.

Preferably, the broadband illumination includes multi-wavelengthillumination including illumination having a number of known wavelengthsat least corresponding to the number of layers in the multilayer object.Additionally, the analyzing includes generating an emerging illuminationintensity map for each of a number of known wavelengths at leastcorresponding in number to the number of layers in the multilayerobject. Preferably, the emerging illumination includes at least one ofreflected illumination and transmitted illumination.

There is also provided in accordance with another preferred embodimentof the present invention a method of analyzing a wavefront, including aplurality of different wavelength components, after the wavefront exitsan object, the method including obtaining a plurality of differentlyphase changed transformed wavefronts corresponding to a wavefront beinganalyzed which has an amplitude and a phase, including applying atransform to each of the plurality of different wavelength components,thereby to generate a plurality of transformed wavefront components andapplying a plurality of scalable phase changes to the plurality oftransformed wavefront components respectively, obtaining a plurality ofintensity maps of the plurality of phase changed transformed wavefrontsand employing the plurality of intensity maps to obtain an outputindicating the amplitude and phase of the wavefront being analyzed.

Preferably, the plurality of scalable phase changes are each in adifferent plane. Additionally, the plurality of different wavelengthcomponents are generated by light sources disposed at various distancesfrom the object.

There is further provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts and employing theplurality of intensity maps to obtain an output indicating the amplitudeand phase of the wavefront being analyzed, wherein obtaining a pluralityof differently phase changed transformed wavefronts includes applying atransform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and the applying aplurality of different phase changes includes providing an opticalsystem having a selectable plurality of optical configurations creatinga corresponding plurality of phase changes respectively.

There is also provided in accordance with still another preferredembodiment of the present invention a method for effecting phase changeof a wavefront including applying a plurality of different phase changesto the wavefront, thereby to obtain a plurality of differently phasechanged wavefronts, wherein the step of applying a plurality ofdifferent phase changes includes providing an optical system having aselectable plurality of optical configurations creating a correspondingplurality of phase changes respectively.

In accordance with yet another preferred embodiment of the presentinvention the optical system includes a spatial light modulator (SLM)including a central inactive area and a peripheral active area.Alternatively, the optical system includes a phase plate having aplurality of portions each corresponding to an individual phase changeand a phase plate portion selector operative to position a selected oneof the phase plate portions along a light path.

Additionally or alternatively, the optical system includes two mirrorsat an adjustable distance from one another whose relative configurationis such that a first portion of the light impinging at the two mirrorconfiguration arrives at the first mirror and a second portion of thelight impinging at the two mirror configuration arrives at the secondmirror. Preferably, the two mirrors include a first mirror preceding asecond mirror along the light path and having an aperture definedtherewith, thereby allowing the second portion of the light to reach thesecond mirror via the aperture. Alternatively, the two mirrors include afirst mirror preceding a second mirror along the light path wherein atleast one dimension of the first mirrors surface area is less than atleast one corresponding dimension of the cross-section of the wavefrontand less than the corresponding dimension of the second mirror's surfacearea, thereby allowing the second portion of the light to reach thesecond mirror. Preferably, the optical system also includes at least onepiezo-electric actuator operative to allow a user to control thedistance between the two mirrors.

There is further provided in accordance with another preferredembodiment of the present invention an apparatus for wavefront analysisincluding a light source, to illuminate an object and to obtain awavefront having an amplitude and a phase, a wavefront transformer,obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed having a phaseand an amplitude, including a transformed wavefront generator, applyinga transform to the wavefront being analyzed thereby to obtain atransformed wavefront and a phase changer, applying a plurality ofdifferent phase changes to the transformed wavefront, thereby to obtaina plurality of differently phase changed transformed wavefronts, anintensity map provider, obtaining a plurality of intensity maps of theplurality of phase changed transformed wavefronts by phase manipulationand an intensity map utilizer, employing the plurality of intensity mapsto obtain an output indicating the amplitude and phase of the wavefrontbeing analyzed, wherein the plurality of different phase changes areapplied to a region of the transformed wavefront, corresponding to ashape of the light source.

There is also provided in accordance with yet another preferredembodiment of the present invention an apparatus for wavefront analysisincluding a light source used to illuminate an object and to obtain awavefront having an amplitude and a phase, a wavefront transformer,obtaining a plurality of differently phase changed transformedwavefronts corresponding to the wavefront being analyzed, including atransformed wavefront generator, applying a transform to the wavefrontbeing analyzed thereby to obtain a transformed wavefront and a phasechanger, applying a plurality of different phase changes to thetransformed wavefront, thereby to obtain a plurality of differentlyphase changed transformed wavefronts, an intensity map provider,obtaining a plurality of intensity maps of the plurality of phasechanged transformed wavefronts by phase manipulation and an intensitymap utilizer, employing the plurality of intensity maps to obtain anoutput indicating the amplitude and phase of the wavefront beinganalyzed, wherein the plurality of different phase changes are appliedto regions of the transformed wavefront, corresponding to a grating.

There is also provided in accordance with still another preferredembodiment of the present invention an apparatus for wavefront analysisincluding a wavefront transformer, obtaining a plurality of differentlyphase changed transformed wavefronts corresponding to a wavefront beinganalyzed which has an amplitude and a phase, an intensity map provider,obtaining a plurality of intensity maps of the plurality of phasechanged transformed wavefronts and an intensity map utilizer, employingthe plurality of intensity maps to obtain an output indicating theamplitude and phase of the wavefront being analyzed, wherein obtaining aplurality of differently phase changed transformed wavefronts includesapplying a transform to the wavefront being analyzed thereby to obtain atransformed wavefront and applying a plurality of different phasechanges to the transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein thetransformed wavefront includes a plurality of different polarizationcomponents and the plurality of different phase changes are effected byusing a birefringent phase changer to apply different phase changes tothe plurality of different polarization components of the transformedwavefront.

There is further provided in accordance with a further preferredembodiment of the present invention an apparatus for wavefront analysisincluding a wavefront transformer, obtaining two differently phasechanged transformed wavefronts corresponding to a wavefront beinganalyzed which has an amplitude and a phase, an intensity map provider,obtaining two intensity maps of the two phase changed transformedwavefronts, and an intensity map utilizer, employing the two intensitymaps to obtain an output indicating the amplitude and phase of thewavefront being analyzed, and wherein the intensity map provider is alsooperative for employing interference between the two intensity maps togenerate a third intensity map and the obtaining two differently phasechanged transformed wavefronts includes applying a transform to thewavefront being analyzed thereby to obtain a transformed wavefront andapplying a plurality of different phase changes to the transformedwavefront, thereby to obtain a plurality of differently phase changedtransformed wavefronts.

There is yet further provided in accordance with another preferredembodiment of the present invention an apparatus for providingsimultaneous surface and layer thickness measurements of a multilayerobject including an illuminator, illuminating the multilayer object withbroadband illumination, an illumination analyzer, analyzing illuminationreflected from the multilayer object to provide a spectral analysisoutput and a spectral analysis utilizer, utilizing the spectral analysisoutput, simultaneously to provide surface and layer thicknessinformation regarding the multilayer object.

There is still further provided in accordance with another preferredembodiment of the present invention a method of object analysisincluding obtaining a first wavefront which has an amplitude and a phasefrom a first sub-surface on the surface of an object, obtaining a secondwavefront which has an amplitude and a phase from a second sub-surfaceon the surface of the object adjacent to the first sub-surface, applyinga plurality of different phase changes to the second wavefront, therebyto obtain a plurality of differently phase changed wavefrontscorresponding to the second wavefront, obtaining a plurality ofintensity maps of the interference of the first wavefront and theplurality of phase changed wavefronts and employing the plurality ofintensity maps to obtain an output indicating the object surface.

There is even further provided in accordance with yet another preferredembodiment of the present invention a method for analyzing a wavefrontincluding using an iris to block off a portion of a wavefront, therebyto generate a wavefront being analyzed having an amplitude and a phase,applying a transform to the wavefront, thereby obtaining a transformedwavefront, effecting a phase change on the transformed wavefront,thereby generating one phase changed transformed wavefront, obtainingone intensity map of the one phase changed transformed wavefront,generating a first region and a second region of the intensity map,where the first region is located inside an image of the iris and thesecond region is located outside the image of the iris, utilizing thesecond region to obtain a reference wavefront and utilizing thereference wavefront and the first region to obtain an output indicatingthe amplitude and phase of the wavefront being analyzed.

There is also provided in accordance with still another preferredembodiment of the present invention a method for wavefront analysisincluding forming a real image of an object at an image plane, analyzingan image wavefront corresponding to the real image at the image planeand utilizing results of the analyzing to reconstruct an objectwavefront, corresponding to the object.

Preferably, the analyzing takes place following forming the real image.

In accordance with another preferred embodiment of the present inventionthe analyzing an image wavefront includes obtaining a plurality ofdifferently phase changed transformed image wavefronts corresponding toan image wavefront being analyzed which has an amplitude and a phase,obtaining a plurality of intensity maps of the plurality of phasechanged transformed image wavefronts and employing the plurality ofintensity maps to obtain an output indicating the amplitude and phase ofthe image wavefront being analyzed.

Preferably, the analyzing an image wavefront includes interfering thewavefront with a wavefront reflected from a reference surface.Additionally, the analyzing an image wavefront includes spatiallysplitting the wavefront into two parts and interfering one part with theother in a common-path manner.

There is further provided in accordance with another preferredembodiment of the present invention a wavefront analysis systemincluding an imager, forming a real image of an object at an imageplane, a wavefront analyzer, analyzing an image wavefront correspondingto the real image at the image plane and an object wavefrontreconstructor, utilizing an output of the image wavefront analyzer toreconstruct an object wavefront, corresponding to the object.

In accordance with another preferred embodiment, the wavefront analyzerincludes a wavefront transformer, operative to provide a plurality ofdifferently phase changed transformed wavefronts corresponding to theimage wavefront which has an amplitude and a phase, an intensity mapgenerator, operative to provide a plurality of intensity maps of theplurality of phase changed transformed wavefronts and an intensity maputilizer, employing the plurality of intensity maps to provide an outputindicating the amplitude and phase of the image wavefront.

There is yet further provided in accordance with still another preferredembodiment of the present invention an apparatus for wavefront analysisincluding an imaging system, generating a wavefront to be analyzed whichhas an amplitude and a phase, a wavefront transformer, operative toprovide a plurality of differently phase changed transformed wavefrontscorresponding to the wavefront being analyzed, an intensity mapgenerator, operative to provide a plurality of intensity maps of theplurality of phase changed transformed wavefronts and an intensity maputilizer, employing the plurality of intensity maps to provide an outputindicating the amplitude and phase of the wavefront being analyzed.

In accordance with still another preferred embodiment of the presentinvention, the system also includes a wavefront interference generator,generating an interference of the wavefront with a wavefront reflectedfrom a reference surface. Additionally or alternatively, the system alsoincludes a wavefront splitter, spatially splitting the image wavefrontinto first and second parts and a wavefront interference generator,generating an common-path interference of the first part with the secondpart.

In accordance with yet another preferred embodiment, the imager is anoptical microscope. Alternatively, the imager is a revolving turret withat least one commercial objective. Preferably, the image plane is anyplane.

Additionally, the wavefront transformer includes an optical manipulatorand an imaging optics and the intensity map generator includes a CCDcamera.

There is also provided in accordance with still another preferredembodiment of the present invention a method of optical propertyanalysis of an object by analyzing a wavefront exiting the object, themethod including providing an imaging system having a defined depth offocus, repeating the following steps focusing on each of several depthswithin the object: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas an amplitude and a phase and which is exiting an object, obtaining aplurality of intensity maps of the plurality of phase changedtransformed wavefronts and employing the plurality of intensity maps toobtain an output indicating the amplitude and phase of the wavefrontbeing analyzed and combining the several outputs generated by repeatingthe obtaining and employing steps in order to obtain a slice-by-sliceoptical transmission profile of the object.

Preferably, the optical transmission profile includes an optical pathlength for each of the several depths within the object.

There is also provided in accordance with still another preferredembodiment of the present invention a method of wavefront analysisoperative to analyze a wavefront exiting from an object, the methodincluding focusing an imaging system on the object without changing thedistance from the object to the imaging system and obtaining a pluralityof differently phase changed transformed wavefronts corresponding to awavefront being analyzed which has an amplitude and a phase, obtaining aplurality of intensity maps of the plurality of phase changedtransformed wavefronts and employing the plurality of intensity maps toobtain an output indicating the amplitude and phase of the wavefrontbeing analyzed.

There is also provided in accordance with still another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed, obtaining aplurality of intensity maps of the plurality of phase changedtransformed wavefronts and employing the plurality of intensity maps toobtain a modulo 2π output indicating the amplitude and phase of thewavefront being analyzed, wherein the step of employing includescomputing at least one characteristic of the object's surface geometryby analyzing a Moiré pattern generated by projecting stripes on theobject and viewing the object through a grating; and resolving the 2πambiguity of the modulo 2π output using at least one characteristic ofthe object's surface geometry.

Preferably, the stripes are generally linear. Additionally, the step ofprojecting stripes includes illuminating the object via a grating.Alternatively or additionally, the step of projecting stripes includesusing a plurality of coherent illumination sources to illuminate theobject, thereby to generate an interference pattern on the object.

In accordance with another preferred embodiment of the present inventionthe object wavefront is a surface mapping wavefront obtained byreflecting radiation from a surface of the object, the surface mappingwavefront having an amplitude and a phase, the image wavefront is animage surface mapping wavefront and the output indicating the amplitudeand phase of the image wavefront being analyzed is employed to obtain anoutput indicating the surface of the object.

Alternatively, the object wavefront is an object inspection wavefrontobtained by transmitting radiation through the object, the objectinspection wavefront having an amplitude and a phase, the imagewavefront is an image object inspection wavefront and the outputindicating the amplitude and phase of the image wavefront being analyzedis employed to obtain an output indicating optical and thicknessproperties of the object.

Alternatively, the object wavefront is a spectral analysis wavefrontobtained by causing radiation to impinge on an object, the spectralanalysis wavefront having an amplitude and a phase, the image wavefrontis an image spectral analysis wavefront and the output indicating theamplitude and phase of the image wavefront being analyzed is employed toobtain an output indicating spectral content of the radiation.

There is further provided in accordance with another preferredembodiment of the present invention a method for wavefront analysisutilizing a propagated wavefront, the method including utilizing apropagated wavefront, which corresponds to a wavefront being analyzed,having an amplitude and a phase, for obtaining an amplitude and a phaseof the propagated wavefront, utilizing the amplitude and phase of thepropagated wavefront to obtain an output indicating the amplitude andphase of the wavefront being analyzed.

There is also provided in accordance with still another preferredembodiment of the present invention a method for wavefront analysisutilizing a propagated wavefront, the method including utilizing apropagated wavefront, which corresponds to a wavefront being analyzed,having an amplitude and a phase, for obtaining a plurality ofdifferently phase changed transformed propagated wavefronts, obtaining,a plurality of intensity maps of the plurality of phase changedtransformed propagated wavefronts and employing the plurality ofintensity maps to obtain an output indicating the amplitude and phase ofthe wavefront being analyzed.

Preferably, the employing includes employing the plurality of intensitymaps to obtain an output corresponding to the propagated wavefront andemploying the output corresponding to the propagated wavefront to obtainan output indicating the amplitude and phase of the wavefront beinganalyzed. Alternatively or additionally, the method also includesutilizing the output indicating the amplitude and phase of the wavefrontbeing analyzed in order to obtain a second output indicating amplitudeand phase of a propagated wavefront obtained by propagating thewavefront being analyzed to any given plane. Additionally, thepropagating the wavefront being analyzed to any given plane alsoincludes propagating through optical elements.

There is still further provided in accordance with yet another preferredembodiment of the present invention a method for wavefront analysisincluding in a first mode of operation: obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to anwavefront being analyzed which has an amplitude and a phase, obtaining aplurality of intensity maps of the plurality of phase changedtransformed wavefronts and employing the plurality of intensity maps toobtain an output indicating the amplitude and phase of the wavefrontbeing analyzed and in a second mode of operation: carrying out aninterferometric measurement on the wavefront being analyzed employing areference in order to provide an output indicating the location of asource of the wavefront being analyzed.

Preferably, the source of the wavefront being analyzed includes anobject. Additionally, the reference includes a mirror.

There is yet further provided in accordance with another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a wavefront being analyzed which has an amplitudeand a phase, obtaining a modified wavefront which has an amplitude and aphase in which estimated known differences of the wavefront beinganalyzed from a planar-like wavefront are removed by an optical element,obtaining a plurality of differently phase changed transformed modifiedwavefronts corresponding to the modified wavefront, obtaining aplurality of intensity maps of the plurality of phase changedtransformed modified wavefronts, employing the plurality of intensitymaps to obtain an output indicating the amplitude and phase of themodified wavefront and obtaining an output indicating the amplitude andphase of the wavefront being analyzed, by reintroducing the estimatedknown differences from the planar-like wavefront to the outputindicating the amplitude and phase of the modified wavefront.

There is also provided in accordance with yet another preferredembodiment of the present invention a wavefront analysis systemincluding a wavefront generator, operative to obtain a wavefront beinganalyzed which has an amplitude and a phase, an optical element,operative to modify the wavefront to obtain a modified wavefront whichhas an amplitude and a phase in which estimated known differences of thewavefront being analyzed from a planar-like wavefront are removed by theoptical element, a phase changer, operative to provide a plurality ofdifferently phase changed transformed modified wavefronts correspondingto the modified wavefront, an intensity map generator, operative togenerate a plurality of intensity maps of the plurality of phase changedtransformed modified wavefronts, an intensity map utilizer, employingthe plurality of intensity maps to provide an output indicating theamplitude and phase of the modified wavefront and a wavefrontreconstructor, operative to obtain an output indicating the amplitudeand phase of the wavefront being analyzed by reintroducing the estimatedknown differences from the planar-like wavefront to the outputindicating the amplitude and phase of the modified wavefront.

In accordance with another preferred embodiment the wavefront beinganalyzed is approximately a spherical wavefront and the optical elementis a lens operative to remove the spherical components of the wavefrontbeing analyzed. Alternatively, the wavefront being analyzed is a tiltedwavefront with additional features and the optical element is a prismoperative to remove the tilt component of the wavefront being analyzed.

There is further provided in accordance with still another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has apolarization, obtaining a plurality of intensity maps of the pluralityof phase changed transformed wavefronts and employing the plurality ofintensity maps to obtain an output indicating the polarization of thewavefront being analyzed.

There is also provided in accordance with yet another preferredembodiment of the present invention a method of wavefront analysisincluding obtaining a plurality of differently polarization changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas a polarization, obtaining a plurality of intensity maps of theplurality of polarization changed transformed wavefronts and employingthe plurality of intensity maps to obtain an output indicating thepolarization of the wavefront being analyzed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a simplified partially schematic, partially pictorialillustration of wavefront analysis functionality used in embodiments ofthe present invention;

FIG. 2 is a simplified partially schematic, partially block diagramillustration of a wavefront analysis system suitable for carrying outthe functionality of FIG. 1;

FIG. 3 is a simplified functional block diagram illustration of part ofthe functionality of FIG. 1;

FIG. 4 illustrates another preferred embodiment of the presentinvention, introducing a line phase delay using a filter in a Fourierplane in conjunction with a line light source;

FIG. 5 illustrates a further preferred embodiment of the presentinvention, introducing a one-dimensional phase grating in a Fourierplane;

FIG. 6 illustrates the replicated image obtained in the Fourier plane inthe embodiment of FIG. 5;

FIG. 7 illustrates the replicated image obtained using different lateralshifts for different wavelengths in accordance with another preferredembodiment of the present invention,

FIG. 8 is a simplified partially schematic, partially block diagram of awavefront analysis system, providing for phase manipulations by means ofpolarization, constructed and operative in accordance with a preferredembodiment of the present invention;

FIG. 9 is a simplified partially schematic illustration of a wavefrontanalysis apparatus where two images interfere, constructed and operativein accordance with yet another preferred embodiment of the presentinvention;

FIG. 10 is a simplified schematic illustration of part of a wavefrontanalysis system using multiple channels for different phase shifts,constructed and operative in accordance with another embodiment of thepresent invention;

FIG. 11 is a simplified schematic illustration of a system for analysis,detection and measurement of multilayer objects, constructed andoperative in accordance with a further preferred embodiment of thepresent invention;

FIG. 12 is a simplified schematic illustration of a wavefront analysissystem using a combination of reflection and transmission modes in phaseshifts, constructed and operative in accordance with another embodimentof the present invention;

FIG. 13 is a simplified schematic illustration of a wavefront analysissystem using scaled phase plates in phase manipulations, constructed andoperative in accordance with still another preferred embodiment of thepresent invention;

FIG. 14 is a simplified schematic illustration of a tunable spatiallight modulator with an active area surrounding an inactive area,constructed and operative in accordance with yet another preferredembodiment of the present invention;

FIG. 15 is a simplified schematic illustration of a spatial lightmodulator comprising two mirrors, in accordance with yet anotherpreferred embodiment of the present invention;

FIG. 16 is a simplified schematic illustration of an implementation ofan improved common path Michelson interferometer, constructed andoperative in accordance with still another embodiment of the presentinvention;

FIG. 17 is a simplified illustration of light reflecting from a diskbeing scanned in accordance with yet another preferred embodiment of thepresent invention;

FIG. 18 is a simplified schematic illustration of a wavefront analysismethod and system using a single intensity map, constructed andoperative in accordance with another preferred embodiment of the presentinvention;

FIG. 19 is a simplified illustration of an illumination pattern obtainedusing an iris in the wavefront analysis system of FIG. 18;

FIG. 20 is a simplified partially schematic, partially pictorialillustration of a system for surface mapping, employing thefunctionality and structure of FIGS. 1 and 2;

FIG. 21 is a simplified partially schematic, partially pictorialillustration of an object inspection system, employing the functionalityand structure of FIGS. 1 and 2;

FIG. 22 is a simplified partially schematic, partially pictorialillustration of a system for spectral analysis, employing thefunctionality and structure of FIGS. 1 and 2;

FIG. 23 is a simplified illustration of combining a wavefront analysissystem and an optical imaging system, constructed and operative inaccordance with yet another preferred embodiment of the presentinvention;

FIG. 24 is a general block diagram of the components of a preferredembodiment of a wavefront analysis module performing the imagedwavefront analysis functionality of FIG. 23;

FIG. 25 is a simplified partially schematic, partially block diagramillustration of a wavefront analysis system including an imagingfunctionality and a phase manipulated based imaged wavefront analysisfunctionality of the type described in FIG. 23;

FIG. 26 is a simplified partially schematic, partially block diagramillustration of a wavefront analysis system operating on an imagedwavefront and forming the imaged wavefront analysis functionality ofFIG. 23;

FIG. 27 is a simplified partially schematic, partially pictorialillustration of a system for surface mapping, employing thefunctionality and structure of FIG. 25;

FIG. 28 is a simplified partially schematic, partially pictorialillustration of a system for object inspection employing thefunctionality and structure of FIG. 25;

FIG. 29 is a simplified partially schematic, partially pictorialillustration of a system for spectral analysis employing thefunctionality and structure of FIG. 25;

FIG. 30 is a general block diagram of the components of a preferredembodiment of a wavefront analysis module performing the imagedwavefront analysis functionality of FIG. 25;

FIG. 31 is a simplified illustration of an existing microscope includinga wavefront analysis module, in accordance with still another preferredembodiment of the present invention;

FIG. 32 is a simplified partially schematic, partially pictorialillustration of a wavefront analysis system operative to generatemeasurements in an extended Z range, constructed and operative inaccordance with yet another preferred embodiment of the presentinvention; and

FIG. 33 is a simplified, partially schematic, partially pictorialillustration of a wavefront analysis system operative to provide theabsolute location of an object with respect to a reference mirror,constructed and operative in accordance with still another preferredembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The methodologies and systems for wavefront analysis, as well as forsurface mapping, phase change analysis, spectral analysis, objectinspection, stored data retrieval, three-dimensional imaging and othersuitable applications utilizing wavefront analysis, describedhereinbelow, may, but need not necessarily, include techniques describedin PCT Patent Application No. PCT/IL/01/00335, dated Apr. 11, 2001, ofthe present assignee, the disclosure of which is hereby incorporated byreference.

Reference is now made to FIG. 1, which is a simplified partiallyschematic, partially pictorial illustration of wavefront analysisfunctionality. The functionality of FIG. 1 can be summarized asincluding the following sub-functionalities: obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to awavefront being analyzed, which has an amplitude and a phase; obtaininga plurality of intensity maps of the plurality of phase changedtransformed wavefronts; and employing the plurality of intensity maps toobtain an output indicating at least one and possibly both of the phaseand the amplitude of the wavefront being analyzed.

As seen in FIG. 1, the first sub-functionality may be realized by thefollowing functionalities: a wavefront, which may be represented by aplurality of point sources of light, is generally designated byreference numeral 100. Wavefront 100 has a phase characteristic which istypically spatially non-uniform, shown as a solid line and indicatedgenerally by reference numeral 102. Wavefront 100 also has an amplitudecharacteristic which is also typically spatially non-uniform, shown as adashed line and indicated generally by reference numeral 103. Such awavefront may be obtained in a conventional manner by receiving lightfrom any object, such as by reading an optical disk, for example a DVDor compact disk 104.

The principal purpose of the method is to measure the phasecharacteristic, such as that indicated by reference numeral 102, and theamplitude characteristic, such as that indicated by reference numeral103, in an enhanced manner.

A transform, indicated here symbolically by reference numeral 106, isapplied to the wavefront being analyzed 100, thereby to obtain atransformed wavefront, symbolically indicated by reference numeral 108.A plurality of different phase changes, preferably spatial phasechanges, represented by optical path delays 110, 112 and 114 are appliedto the transformed wavefront 108, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, represented byreference numerals 120, 122 and 124 respectively. It is appreciated thatthe illustrated difference between the individual ones of the pluralityof differently phase changed transformed wavefronts is that portions ofthe transformed wavefront are delayed differently relative to theremainder thereof.

The second sub-functionality may be realized by applying a transform,preferably a Fourier transform, to the plurality of differently phasechanged transformed wavefronts. Finally, this sub-functionality requiresdetection of the intensity characteristics of the plurality ofdifferently phase changed transformed wavefronts. The outputs of suchdetection are the intensity maps, examples of which are designated byreference numerals 130, 132 and 134.

The third sub-functionality may be realized by the followingfunctionalities: expressing, such as by employing a computer 136, theplurality of intensity maps, such as maps 130, 132 and 134, as at leastone mathematical function of phase and amplitude of the wavefront beinganalyzed and of the plurality of different phase changes, wherein atleast one, and possibly both, of the phase and the amplitude are unknownand the plurality of different phase changes, typically represented byoptical path delays 110, 112 and 114 to the transformed wavefront 108,are known; and employing, such as by means of the computer 136, the atleast one mathematical function to obtain an indication of at least one,and possibly both, of the phase and the amplitude of the wavefront beinganalyzed, here represented by the phase function designated by referencenumeral 138 and the amplitude function designated by reference numeral139, which, as can be seen, respectively represent the phasecharacteristics 102 and the amplitude characteristics 103 of thewavefront 100. Wavefront 100 may represent the information contained orthe height map of the measured object, such as compact disk or DVD 104in this example.

Reference is now made to FIG. 2, which is a simplified partiallyschematic, partially block diagram illustration of a wavefront analysissystem suitable for carrying out the functionality of FIG. 1.

As seen in FIG. 2, a wavefront, here designated by reference numeral150, is focused, as by a lens 152, onto a phase manipulator 154, whichis preferably located at the focal plane of lens 152. The phasemanipulator 154 generates phase changes, and may be, for example, aspatial light modulator or a series of different transparent, spatiallynon-uniform objects. A second lens 156 is arranged so as to imagewavefront 150 onto a detector 158, such as a CCD detector. Preferablythe second lens 156 is arranged such that the detector 158 lies in itsfocal plane. The output of detector 158 is preferably supplied to datastorage and processing circuitry 160, which preferably carries out thethird sub-functionality described hereinabove with reference to FIG. 1.

Reference is now made to FIG. 3, which is a simplified functional blockdiagram illustration of part of the functionality of FIG. 1, wherein thetransform applied to the wavefront being analyzed is a Fouriertransform, wherein at least three different spatial phase changes areapplied to the thus transformed wavefront, and wherein at least threeintensity maps are employed to obtain indications of at least one of thephase and the amplitude of the wavefront. As seen in FIG. 3, anddescribed in the third sub-functionality hereinabove with reference inFIG. 1, the intensity maps are employed to obtain an output indicationof at least one and possibly both of the phase and the amplitude of thewavefront being analyzed. FIG. 3 illustrates the general principles ofthe algorithms and computation methods used to analyze the wavefront.

Turning to FIG. 3, it is seen that the wavefront being analyzed isexpressed as a first complex function ƒ(x)=A(x)e^(iφ(x)), indicated byreference numeral 300, where ‘x’ is a general indication of a spatiallocation. The complex function has an amplitude distribution A(x) and aphase distribution φ(x) identical to the amplitude and phase of thewavefront being analyzed. Each of the plurality of different spatialphase changes is applied to the transformed wavefront, preferably byapplying a spatially uniform spatial phase delay, having a known value,to a given spatial region of the transformed wavefront. As seen in FIG.3, the spatial function governing these different phase changes isdesignated by ‘G’, an example of which, for a phase delay value of θ, isdesignated by reference numeral 304. Function ‘G’ is a spatial functionof the phase change applied in each spatial location of the transformedwavefront. In the specific example 304, the spatially uniform spatialphase delay, having a value of θ, is applied to a spatially centralregion of the transformed wavefront, as indicated by the central part ofthe function having a value of θ, which is greater than the value of thefunction elsewhere.

A plurality of expected intensity maps, indicated by spatial functionsI₁(x), I₂(x) and I₃(x), are each expressed as a function of the firstcomplex function f(x) and of the spatial function ‘G’, as indicated byreference numeral 309. Subsequently, a second complex function S(x),which has an absolute value |S(x)| and a phase α(x), is defined as aconvolution of the first complex function f(x) and of a Fouriertransform of the spatial function ‘G’. This second complex function,designated by reference numeral 312, is indicated by the equationS(x)=ƒ(x)*ℑ(G)=|S(x)|e^(iα(x)), where the symbol ‘*’ indicatesconvolution and ℑ(G) is the Fourier transform of the function ‘G’. Thedifference between φ(x), the phase of the wavefront, and α(x), the phaseof the second complex function, is indicated by ψ(x), as designated byreference numeral 316.

The expression of each of the expected intensity maps as a function off(x) and G, as indicated by reference numeral 308, the definition of theabsolute value and the phase of S(x), as indicated by reference numeral312 and the definition of ψ(x), as indicated by reference numeral 316,enables expression of each of the expected intensity maps as a thirdfunction of the amplitude of the wavefront A(x), the absolute value ofthe second complex function |S(x)|, the difference between the phase ofthe wavefront and the phase of the second complex function ψ(x), and theknown phase delay produced by one of the at least three different phasechanges which each correspond to one of the at least three intensitymaps. This third function is designated by reference numeral 320 andincludes three functions, each preferably having the general form

I_(n)(x) = A(x) + (𝕖^(𝕚 θ_(n)) − 1)S(x)𝕖^(−𝕚 ψ(x))²where I_(n)(x) are the expected intensity maps and n=1, 2 or 3. In thethree functions, θ₁, θ₂ and θ₃ are the known values of the uniformspatial phase delays, each applied to a spatial region of thetransformed wavefront, thus effecting the plurality of different spatialphase changes which produce the intensity maps I₁(x), I₂(x) and I₃(x),respectively. It is appreciated that preferably the third function atany given spatial location x₀ is a function of A, ψ and |S| only at thesame spatial location x₀. The intensity maps are designated by referencenumeral 324.

The third function is solved for each of the specific spatial locationsx₀, by solving at least three equations, relating to at least threeintensity values I₁(x₀), I₂(x₀) and I₃(x₀) at at least three differentphase delays θ₁, θ₂ and θ₃, thereby to obtain at least part of threeunknowns A(x₀), |S(x₀)| and ψ(x₀). This process is typically repeatedfor all spatial locations and results in obtaining the amplitude of thewavefront A(x), the absolute value of the second complex function |S(x)|and the difference between the phase of the wavefront and the phase ofthe second complex function ψ(x), as indicated by reference numeral 328.Thereafter, once A(x), |S(x)| and ψ(x) are known, the equation definingthe second complex function, represented by reference numeral 312, istypically solved globally for a substantial number of spatial locations‘x’ to obtain α(x), the phase of the second complex function, asdesignated by reference numeral 332. Finally, the phase φ(x) of thewavefront being analyzed is obtained by adding the phase α(x) of thesecond complex function to the difference ψ(x) between the phase of thewavefront and the phase of the second complex function, as indicated byreference numeral 336.

Reference is now made to FIG. 4, which illustrates another embodiment ofthe present invention, for reducing the spatial coherence, such as byutilizing a light source having a special form, such as a line lightsource. An imaging system working with spatially coherent light is verynoisy due to fringes from many sources, such as interference patternsbetween different layers in the optical path and particles and scratchedalong the optical path. It is desirable to reduce the spatial coherenceof light in order to eliminate the fringes and to increase the lateralresolution. However, to obtain the plurality of intensity maps out ofthe plurality of phase changed transformed wavefronts, spatiallycoherent light is preferred. Spatial coherence is preferred over thewavefront to which spatial phase change is applied. Preferably, thelight source should have spatial coherence in one-dimension only. Thiscan be accomplished, for instance, by using a line light source insteadof a point light source. This line-light source can be used either toreflect light from an inspected object or to transmit light through apartially transparent inspected object. Additionally, the spatialfunction of the phase change applied in each spatial location of thetransformed wavefront, designated ‘G’ hereinabove in reference to FIG.3, is preferably a line-function, generating a spatially uniform spatialphase delay in a region having a ‘line-like’ (elongated) shape ofrelatively small width passing through the center region of thetransformed wavefront. This line spatial function, in conjunction withthe line light-source, reduces the computation algorithms to be verysimilar to the computation algorithms as described hereinabove.

The embodiment of FIG. 4 illustrates reducing the spatial coherence byintroducing a line phase delay using a filter in a Fourier plane inconjunction with a line light source. As seen in FIG. 4, light isprojected from a line light source 400 through an object 402. Theresulting wavefront is focused, as by a lens 404, onto a line phasemanipulator 406, preferably located at the focal plane of lens 402. Asecond lens 408 is arranged so as to image the wavefront onto a detector410, such as a camera or CCD detector. Preferably the second lens 408 isarranged such that the detector 410 lies in its focal plane. The outputof detector 410 is subsequently processed by a data storage andprocessing unit 412. In an alternative embodiment, not illustrated, thelight may be reflected from the object 402.

In the configuration seen in FIG. 4 and described hereinabove, thespatial coherence in the Y dimension is eliminated. In the image plane,obtained on the surface of the camera 410, the convolution of the object402 and the Fourier transform of the filter is obtained for only the Xdimension and not for the Y dimension. Therefore, the calculationsrequired for measurement of the inspected object 402, i.e. obtaining thephase and amplitude of the wavefront being analyzed, need to beperformed only in one dimension and not in the two dimensions.Additionally, the measurement and analysis system is much less sensitiveto tilts of the inspected object, either by reflection or transmission,in the Y axis. The inspected object 402 can subsequently be rotated todecrease the tilt sensitivity in the other dimension. It should be clearthat a “line” is only one example of the shape of the light source, andany shape other than point source affects the coherence and can thus beused, provided that the phase change filter has a substantially similarform.

The calculations required for a measurement of an object or analysis ofa wavefront using a one-dimensional filter in a Fourier plane aredescribed below:

The complex electric field transmitted or reflected by the object, whichis the wavefront to be analyzed is described by equation 4.1.ƒ(x,y)=A(x,y)exp[iφ(x,y)]  (4.1)

The field obtained in the Fourier plane is described by equation 4.2.F(u,v)=ℑ[ƒ(x,y)]  (4.2)

The filter function of the one-dimensional phase filter, in the Ydirection, is given by equation 4.3, where δu is the width of the filterin the X direction.

$\begin{matrix}{{G\left( {u,v} \right)} = {1 + {\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack{{rect}\left( \frac{u}{\delta\; u} \right)}}}} & (4.3)\end{matrix}$

The resulting electric field in the Fourier plane after filtering isdescribed by equation 4.4.H(u,v)=F(u,v)·G(u,v)  (4.4)

The electric field in the image plane is the Fourier transform of theelectric field in the Fourier plane, and is described by equation 4.5,where g(x,y) is the Fourier transform of G(u,v) and is described byequation 4.6.h(x,y))=ℑ[H(u,v)]=ƒ(x,y)*g(x,y)  (4.5)g(x,y)=δ(x,y)+[exp(iθ)−1]sin c(δu·x)  (4.6)

Substituting equation 4.3 and 4.6 in equation 4.5 results in equation4.7.h(x,y)=ƒ(x,y)+[exp(iθ)−1]ƒ(x,y)*sinc(δu·x)=ƒ(x,y)+[exp(iθ)−1]S(x,y)  (4.7)

The resulting intensity in the image plane is:l(x,y)=|ƒ(x,y)+[exp(iθ)−1]S(x,y)|²=|A(x,y)exp(iφ(x,y))+[exp(iθ)−1]S(x,y)|²

These equations are very similar to the equations discussed hereinabove,with reference to FIG. 3, except that the convolution is one-dimensionalin the X direction and not in the Y direction.

In order to better obtain the values of |S(x,y)|, a one-dimensionalparabola can be fitted to each line.

This configuration provides several distinct advantages. Thecalculations can be separated to one-dimensional calculations for eachline instead of two-dimensional calculations. The |S(x,y)| function canbe calculated more accurately using the a-priori knowledge that itshould be cylindrical and at a certain direction. Problems associatedwith tilting of the inspected object in one dimensions are minimized.

The sample can be rotated to minimize the tilt problem in the otherdimension as well.

In the configuration described above, the line light source can beviewed as an addition of point light sources. The line light source isparallel to the one-dimensional filter, which is a line filter, thus,each point in the line light source will create its own image on theimage plane. The different images of each point in the one-dimensionallight source have the same intensity distribution in the image plane.The tilt of the point light source corresponding to the optical axisadds a linear phase shift to the wavefront reflected or transmitted bythe object. In the Fourier plane this linear phase shift is transformedto a lateral shift of the DC of the Fourier transform of the object.However, because the phase filter is parallel, the different DCs stillincident on the filter and get the correct phase shift. In the imageplane the square of the Fourier transform, which is actually theintensity of the image, eliminates the linear shift and the sameintensity is obtained for each image. Each point-source of the 1-D lightsource is actually effected by a one-dimensional filter, and thereconstruction algorithms can be done by calculations in one-dimensiononly, as described above. Most of the fringes will disappear due to theelimination of the spatial coherence in one dimension.

Reference is now made to FIG. 5, which illustrates another embodiment ofthe present invention introducing a one-dimensional phase grating in aFourier plane. As seen in FIG. 5, light is projected from a light source(not shown) through an object 502. The resulting wavefront is focused,as by a lens 504, onto a one dimensional phase grating 506, preferablylocated at the focal plane of lens 502. A second lens 508 is arranged soas to image the wavefront onto a detector 510, such as a camera or CCDdetector. Preferably the second lens 508 is arranged such that thedetector 510 lies in its focal plane. The output of detector 510 issubsequently processed by a data storage and processing unit 512.

When a one-dimensional or two-dimensional phase grating is introduced inthe Fourier plane, or a different plane of the imaging system, of thewavefront analysis system, a replicated image is obtained in the imageplane. This replication is one-dimensional or two-dimensional, dependingon the grating 506, since the image replication is parallel to thereplication of the grating 506. The grating's period defines theoverlapping of the replicated images. In the case of a one-dimensionalgrating 506, an example of the grating's period that can be chosen is aperiod that will create only two images overlapped at each point. Thissituation results in images similar to images obtained from shearinginterferometry, where the light from each two points in the image with aconstant distance between them interfere. In the interference of thelight complex amplitudes of the two overlapped points, there are threeunknown variables: the absolute amplitudes of light of each point of theimage and the phase difference. These three unknowns can be obtainedlocally by measuring the intensities in these points with only two phaseshifts introduced by the phase grating:

The calculations required for a measurement of an object or analysis ofa wavefront using a one-dimensional grating in a Fourier plane aredescribed below:

Assuming that the one-dimensional phase grating is in the X dimension,the orating function is described by equation 5.1, where Δu is thegrating spacing and δu is the width of each line in the grating.

$\begin{matrix}{{G\left( {u,v} \right)} = {\left\{ {{{rect}\left( \frac{u}{\Delta\; u} \right)}\left\lbrack {1 + {\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack{{rect}\left( \frac{u}{\delta\; u} \right)}}} \right\rbrack} \right\}*{{comb}\left( \frac{u}{\Delta\; u} \right)}}} & (5.1)\end{matrix}$

The field in the image plane is the Fourier transform of the field inthe Fourier plane and is described in equation 5.2, where f(x,y) is theobject complex amplitude and g(x,y) is the Fourier transform of G(u,v)as described in equation 5.3, where δ(x) is the delta function.h(x,y)=ƒ(x,y)*g(x,y)  (5.2)g(x,y)=sin c(Δu·x)·comb(Δu·x)+[exp(iθ)−1]sinc(δu·x)·comb(Δu·x)=δ(x)+[exp(iθ)−1]sin c(δu·x)·comb(Δu·x)  (5.3)

Substituting equation 5.3 in equation 5.2 results in equation 5.4.h(x,y)=ƒ(x,y)+[exp(iθ)−1]ƒ(x,y)*{sin c(δu·x)·comb(Δu·x)}  (5.4)

The interpretation of equation 5.4 is that the interference pattern iscaused by interference of multiple images, where the image of the objectitself is in the center of the field and a series of complex amplitudesof the image of the object, each displaced by the amount 1/Δu relativeto each other and multiplied by the factor [exp(iθ)−1]sin c(θu·x).

If the object is a square with the dimensions “a” over “a” and if wechoose the grating spacing, Δu, such that

${\frac{1}{\Delta\; u} = \frac{a}{2}},$then only two complex amplitudes overlap. The two complex amplitudes onthe right side of the field are exp(iθ)ƒ(x,y) and

$\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack\sin\;{c\left( {\frac{\pi}{2} \cdot a} \right)}{{f\left( {{x - a},y} \right)}.}$On the left side of the field the two complex amplitudes are exp(iθ)ƒ(x,y) and

$\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack\;\sin\;{c\left( {\frac{\pi}{2} \cdot a} \right)}{{f\left( {{x + a},y} \right)}.}$

Reference is now made to FIG. 6, which illustrates the replicated imageobtained in the Fourier plane. The intensity at point x₁ in the imageplane is the square of the sun of the two overlapped complex amplitudesand is described by equation 5.5, where x₂ is described by equation 5.6and B is the complex number described in equation 5.7.

$\begin{matrix}{I_{1} = {{{{{\exp\left( {{\mathbb{i}}\;\theta} \right)}{f\left( {x_{1},y} \right)}} + {\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack\;\sin\;{c\left( {\frac{\pi}{2} \cdot \; a} \right)}{f\left( {x_{2},y} \right)}}}}^{2}\mspace{20mu} = {{{f\left( {x_{1},y} \right)} + {B \cdot {f\left( {x_{2},y} \right)}}}}^{2}}} & (5.5) \\{x_{2} = {x_{1} + a}} & (5.6) \\{B = {{\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack\;\sin\;{c\left( {\frac{\pi}{2} \cdot a} \right)}{\exp\left( {{- {\mathbb{i}}}\;\theta} \right)}} - {{B}{\exp\left( {{\mathbb{i}}\;\phi} \right)}}}} & (5.7)\end{matrix}$

The intensity at the point x₂ in the image plane is described byequation 5.8.

$\quad\begin{matrix}{I_{2} = {{{{{\exp\left( {{\mathbb{i}}\;\theta} \right)}{f\left( {x_{2},y} \right)}} + {\left\lbrack {{\exp\left( {{\mathbb{i}}\;\theta} \right)} - 1} \right\rbrack\;\sin\;{c\left( {\frac{\pi}{2} \cdot \; a} \right)}{f\left( {x_{1},y} \right)}}}}^{2}\mspace{20mu} = {{{f\left( {x_{2},y} \right)} + {B \cdot {f\left( {x_{1},y} \right)}}}}^{2}}} & (5.8)\end{matrix}$

Equations 5.9 and 5.10 describe the complex amplitudes in the points x₁and x₂ respectively, where ψ1 is the phase of the complex amplitude atthe point x₁, ψ₂ is the phase of the complex amplitude at the point x₂and φ is the phase of B.I ₁=|ƒ(x ₁ ,y)|² +|B·ƒ(x ₂ ,y)|²+2|ƒ(x ₁ ,y)∥B·ƒ(x ₂,y)|cos(ψ₂−ψ₁+φ)  (5.9)I ₂ =|B·ƒ(x ₁ y)|²+|ƒ(x ₂ ,y)|²+2|ƒ(x ₁ ,y)∥B·ƒ(x ₂,y)|cos(ψ₂−ψ₁+φ)  (5.10)

Since there are 3 unknowns: |ƒ(x₁,y)|, |ƒ(x₂,y)| and , ψ₂−ψ₁, anadditional equation is needed. Taking a measurement with no filter, i.e.filter=0, the values of |ƒ(x₁,y)| and |ƒ(x₂,y)| can be measuredimmediately. Another measurement with any filter, using equation 5.9 or5.10, enables the calculation of the phase difference, ψ₂−ψ.

The present preferred configuration requires only two measurements, withdifferent phase delays. Furthermore, the calculations required in orderto extract the measured object, i.e. the analyzed wavefront, are localand straightforward.

The measurements described above, using a grating in the Fourier plane,can be done by two or more wavelengths, for example, when one wavelengthserves for the filter 0, i.e. no phase delay is applied, and anotherwavelength for the second set of measurements. In this configuration thedifferent phase delays are obtained by using two wavelengths, and aconstant phase delay can be used. Additionally, instead of or inaddition to two or more wavelengths, two orthogonal polarizations oflight can be used to generate two different phase delays.

Reference is now made to FIG. 7, which illustrates the replicated imageobtained using different lateral shifts for different wavelengths. Thegrating inserted in the Fourier plane can also be used to enhance thelateral resolution of the measurement or wavefront analysis. The phasegrating introduced in the Fourier plane replicates the image obtained inthe image plane. The grating's period defines the overlapping of thereplicated images. The lateral shift between the replicated images iswavelength dependent, as each wavelength has a different lateral shift.As a result, the object or the wavefront can be reconstructed fordifferent pixel lateral shifts for different wavelengths, as seen inFIG. 7. If the lateral shifts are sub-pixels, a reconstruction withsuper-resolution can be obtained.

The present invention also provides for phase manipulations by means ofpolarization. In the wavefront analysis system and method depictedhereinabove with reference to FIGS. 1 and 2, different intensity imagesare obtained in order to analyze a wavefront or measure an object. Thedifference between the intensity of the images is such that a differentphase shift is introduced to a transformed wavefront, for example,introducing different phase shifts to various frequencies of the objectin the Fourier plane. The different phase shifts can be realized byseveral methods. A preferred method for obtaining the differentintensity images is by using light having several polarizationcomponents. The phase-manipulation filter can thus be made of abirefringent material, resulting in the phase delay of the polarizationcomponent of light propagating through the slow axis being differentfrom the phase delay of the polarization component of light propagatingthrough the fast axis.

In a preferred embodiment of the present invention, three sensors, eachcovered with polarizers having different directions from each other, areused. For example, a first CCD sensor is covered with a polarizer in adirection parallel to the optical axis of the birefringent material, asecond CCD sensor is covered with a polarizer in a directionperpendicular to the optical axis of the birefringent material and athird CCD sensor is covered with a polarizer at a 45°, or any othersuitable, angle to the optical axis of the birefringent material. Thedifferent polarization components of the light will thus have differentphase delays. An interference between the two components of the twopolarizations that pass through the polarizer is generated on the thirdsensor. Using the three intensity images generated on the three sensors,the characteristics of the object can be calculated. The three sensorscan be implemented in a variety of ways, such as three different CCDcameras or a 3-CCD camera having 3′ sensors with suitable polarizers.

Reference is now made to FIG. 8, which is a simplified partiallyschematic, partially block diagram of a wavefront analysis system,providing for phase manipulations by means of polarization, constructedand operative in accordance with yet another preferred embodiment of thepresent invention.

In this embodiment, a single sensor is used, and the differentpolarization components of the light are separated by using polarizationcontrollers along the optical path. As seen in FIG. 8, a complexamplitude having two polarization components 802 passes through apolarizer 804. This complex amplitude of light is the sum of thecomponents of the two orthogonal polarizations in the direction of thepolarizer, as seen by reference numeral 806. The resulting wavefront808, having both polarization components 802, is focused, as by a lens810, onto a phase manipulator 812, made of a birefringent material,which is preferably located at the focal plane of lens 810. The phasemanipulator 812 generates different phase changes to each polarizationcomponent. A second lens 814 is arranged so as to image wavefront 808through a polarization controller 816, onto a detector 818, such as aCCD detector. Preferably the second lens 814 is arranged such that thedetector 818 lies in its focal plane. The output of detector 818 ispreferably supplied to data storage and processing circuitry 820, whichanalyzes the intensity maps to obtain information about wavefront 808,such as its amplitude, phase and polarization. The polarizationcomponent imaged by detector 818 is controlled by the polarizationcontroller 816 in a way that at different times, different polarizationsare imaged. In another preferred embodiment, the polarization controller816 is a rotating polarizer which polarizes the light to differentpolarizations. The measurements are taken one at a time when thedetector 818 is synchronized with the rotation of the polarizer.

In another preferred embodiment of the present invention, three lightbeams with different polarizations from three different light sourcesare used, and the polarization is preserved, such as by a polarizationpreserving fiber. The measurements can then be taken simultaneously withdifferent sensors or at different times with a single sensor.

Some of the calculations required for measurement of an object, oranalysis of a wavefront, while implementing the phase manipulations bydifferent polarizations are described below:

The two orthogonal polarizations propagating through the birefringentphase plate will possess different phase delays. The intensities in theimage plane of the two polarizations are given by equation 8.1, where θ₁and θ₂ are the different phase shifts for the two polarizations.I ₁ =|Ae ^(iψ)+(e ^(iθ) ¹ −1)S| ²I ₂ =|Ae ^(iψ)+(e ^(iθ) ² −1)S| ²  (8.1)

The polarizer of the third camera is placed at a 45° angle, or othersuitable angle, to the optical axis of the birefringent material. Thisresults in an interference between the two components of the twoorthogonal polarizations that pass through the polarizer. The complexamplitudes of the two orthogonal polarizations are given in equations8.2 and 8.3.a ₁ =Ae ^(iψ)+(e ^(iθ) ¹ −1)S  (8.2)a ₂ =Ae ^(iψ)+(e ^(iθ) ² −1)S  (8.3)

When the polarizer is at a 45° angle, the value of these components isdescribed in equation 8.4.

$\quad\begin{matrix}{a_{3} = {{\left\lbrack {{A\;{\mathbb{e}}^{{\mathbb{i}}\;\psi}} + {\left( {{\mathbb{e}}^{{\mathbb{i}}\;\theta_{1}} - 1} \right)S} + {A\;{\mathbb{e}}^{{\mathbb{i}}\;\psi}} + {\left( {{\mathbb{e}}^{{\mathbb{i}\theta}_{2}} - 1} \right)S}} \right\rbrack\cos\; 45}\mspace{25mu} = {{2\left\lbrack {{A\;{\mathbb{e}}^{{\mathbb{i}}\;\psi}} + {\left( {\frac{{\mathbb{e}}^{{\mathbb{i}}\;\theta_{1}} + {\mathbb{e}}^{{\mathbb{i}\theta}_{1}}}{2} - 1} \right)S}} \right\rbrack}\cos\; 45}}} & (8.4)\end{matrix}$

The intensity is the square of the sum of the two complex amplitudes,the value of which is described in equation 8.5.

$\begin{matrix}{I_{3} = {{{A\;{\mathbb{e}}^{{\mathbb{i}}\;\psi}} + {\left( {\frac{{\mathbb{e}}^{{\mathbb{i}}\;\theta_{1}} + {\mathbb{e}}^{{\mathbb{i}\theta}_{1}}}{2} - 1} \right)S}}}^{2}} & (8.5)\end{matrix}$

Equation 8.5 is similar to equation 8.1 and equation 8.2 and can thus besolved as described hereinabove with reference to FIG. 3.

This method provides several distinct advantages. The same wavelengthcan be used for all the images and the same algorithm describedhereinabove with reference to FIG. 3 can also be utilized. There are nomoving parts, no active phase changes and no splitting to the differentchannels of the optical path.

Reference is now made to FIG. 9, which is a simplified partiallyschematic illustration of a wavefront analysis apparatus where twoimages interfere, constructed and operative in accordance with yetanother preferred embodiment of the present invention. In thisembodiment, more data about the complex amplitude in the image plane isobtained by interfering different images with each other and generatingan interference pattern.

In the wavefront analysis or object measurement methods and systemsdescribed hereinabove different intensity images are obtained in theimage plane and utilized for the analysis. In the image plane, there areactually different complex amplitudes, not only different intensities.These complex amplitudes, i.e. an amplitude and phase in each imageplane, are not readily detectable, since the cameras are intensitydetectors, detecting only the absolute value of the complex amplitude.

This embodiment overcomes this problem of detecting the complexamplitudes. An interference image of two images, or two wavefronts,provides an intensity image affected by the phase difference between thetwo interfered complex amplitudes. Thus, instead of three differentphase delays, as described hereinabove with reference to FIGS. 1 and 3,the analysis of a wavefront can be obtained by two intensity maps,obtained by two different phase delays, using the interference of thetwo images as the third intensity map. These three intensity maps arethen utilized, in a method similar to that described hereinabove withreference to FIG. 3, to generate the phase and amplitude of thewavefront. As seen in FIG. 9, channel 1 represents the interferenceimage between channel 2 and channel 3, each having a different phasedelay. Operation of the shutters enable images to be obtained in each ofthe channels as appropriate, thus, when obtaining an image in channel 1,both shutters 2 and 3 are in the open position, while shutter 2 isopened and shutter 3 is closed when obtaining an image in channel 2 andshutter 3 is opened and shutter 2 is closed to obtain an image inchannel 3.

In another embodiment of the present invention, the method is operativeto define confidence levels and perform error correction.

In the method described hereinabove with reference to FIG. 1 and FIG. 2,specifically when the spatial function “G” of FIG. 3 is applied to aspatially central region, the second complex function S(x,y), asdescribed hereinabove, can represent the low frequencies of theinspected object obtained, or the wavefront being analyzed, since it isgenerated by low-pass filtering in the Fourier plane. As a result, thefunction |S(x,y)|² can be approximated by a low degree polynomial, suchas a second order polynomial, of the position. A second degreepolynomial is best fitted to the function |S(x,y)|² resulting from theexperimental results, by best fitting methods, such as least squaresapproximation. It is therefore possible to obtain approximate values for|S(x,y)| over the entire plane from the value of the function at only afew points in the plane. Following this approximation, to every point(x_(i), y_(i)) a ‘confidence level’ can be defined, based on thedifference between the value of the function |S| at the point, and thevalue of the polynomial approximation of |S| at the point. Accordingly,every pixel in the image plane can have a ‘confidence level’, indicativeof the quality of the experimental results, or the noise level, at thispixel. This indication defines a “level of confidence” of the phase andamplitude of the analyzed wavefront calculated at each point.

When there are more than three measurements, i.e. more than 3differently phase changed wavefronts, resulting in more than 3 intensitymaps at the image plane, the level of confidence of each combination ofevery three measurements can be calculated. This level of confidence ateach point can then be used to increase the accuracy of the measurementand minimize the noise by several methods, such as at each pointchoosing the phase and intensity of the wavefront being analyzedcalculated by the three measurements having the maximal level ofconfidence, or averaging the different results from differentcombinations, weighting each result related to the level of confidencein the appropriate combination.

This level of confidence can be used for error correction and noisereduction of the measurement and analysis. The value in each point, orpixel, in the analyzed parameter, such as the phase or amplitude of theanalyzed wavefront, can be modified, for example to maximize the levelof confidence in the same point in |S(x,y)|.

In another embodiment, multiple wavelengths are used, for example, toincrease the dynamic range of the height measurements. The dynamicrange, however, is noise limited. When there is noise, one of theseveral heights that fall within the accuracy of the measurements shouldbe chosen. As described hereinabove, the difference at each point,between the S calculated from the experimental results and the smoothedS calculated by the second degree polynomial, can be used as anindicator for the quality of the experimental results at that point.This indication defines the “level of confidence” of the phasecalculated at each point. The “level of confidence” of each wavelengthis calculated. The phase calculated which has the maximal “level ofconfidence” can be chosen as the “true” phase. For the other wavelength,the height that is closer to the smoothed S can be chosen as the “true”height.

In still another embodiment, a normalization process may be used toincrease the measurement accuracy, when there are different averageintensity levels at each one of the resulting intensity maps. In thisembodiment, the intensities of all the pixels in each of the intensitymaps are summed and the pixels in all but one of the intensity maps aremultiplied by the ratio of the relevant sums. The normalization processcan also be performed when the light source is spectrally broad or notspatially coherent.

Still another normalization method normalizes the halo, or intensity ofS, around the image for the different intensity maps. The halo aroundthe image depends on the object and the spatial form of the phase changeapplied to the transformed wavefront, and does not depend on the valueof the phase change applied to the transformed wavefront.

The wavefront analysis method described hereinabove with reference toFIGS. 1 and 2 can also be used, when reflecting light from ortransmitting light through a known object, to determine the effectivephase change value applied to the transformed wavefront. Additionally,since the contrast of the resulting intensity map is relativelyinsensitive to the normalization, losses, fringes and other noises inthe optical system, but is dependent on the value of the phase change,the effective phase change value can be calculated by measuring thecontrast in the intensity map image of a known object. The phase changevalue resulting in a measured contrast in the image closest to theexpected value is the effective phase change value.

This method can also be used to obtain the effective area and spatialshape in the transformed wavefront in which the phase change is applied.This effective area of the phase can be calculated by extrapolations ofthe zeros of the low order polynomial that describe the function ofS(x).

In accordance with another embodiment of the present invention, a flatmirror can be used to calibrate the wavefront analysis system. In thisembodiment, a known reflected wavefront is generated by using any knownobject, and in particular a flat mirror as the inspected object. Theresulting intensity maps from this known wavefront can be used toperform normalization as described hereinabove between the differentintensity maps obtained, where this normalization will also be valid fordifferent non a-priori known objects. The known wavefront reflected froma flat mirror can also be used as the known wavefront in order to obtainthe effective phase change value or the effective phase change area asdescribed hereinabove. The resulting intensity maps can also be used toeliminate or minimize noise and other error factors in the entiresystem, by subtracting or dividing the resulting intensity maps ofunknown objects by the known intensity maps obtained using the flatmirror.

In yet another embodiment of the present invention, the wavefront to beanalyzed may be obtained using only two different phase changes. In thisembodiment, part of a signal reflected from or transmitted through anobject to be inspected is intentionally blocked, such as by an iris.Information is then obtained from the area of the intensity maps,resulting from a phase changed transformed wavefront, both from theimaging of the unblocked area in the object plane and the area outsidethe image of the iris. The intensity outside the iris can be shown to beequivalent to the absolute value squared of the object low pass (|S|² inreference to FIG. 3). Using a polynomial approximation, such as a seconddegree polynomial, of this absolute value squared to in the position,the value of |S(x,y)| can be obtained over the entire plane. Thisprovides one of the unknowns required in the algorithm as describedhereinabove with reference to FIG. 3, thus, only two intensity maps arerequired, and therefore only two phase changes need to be applied.

In accordance with still another embodiment, some of the wavefront isblocked, such as by an iris, and data is obtained from the intensity mapin an area outside the image of the iris. The minimum spot size of anoptical imaging system is a function of the wavelength and the numericalaperture, or F/#, of the optical system. In order to set the spot sizeof the optical system, the effective numerical aperture can be partiallycontrolled by the field of view in the object plane. This field of viewcan be set by introducing an iris in the object plane, or in a planeimaging the object. During the imaging process, the object within theiris is imaged to an image limited by the iris image. An iris can beintroduced in an implementation of the wavefront analysis system asdescribed hereinabove with reference to FIGS. 1 and 2. Intensityinformation exists outside the image of the object, creating a “halo”around the iris image, outside the iris, by the diffraction of lightfrom the phase manipulation, such as the Fourier filter. This halo canbe used to obtain additional information regarding the wavefront beinganalyzed. The intensity of the halo is the absolute square of thelow-pass frequencies of the object outside the halo. This can help inreconstructing the S(x) function described hereinabove. A low orderpolynomial is best fitted to the intensity of the halo. When a flatobject is used for calibration, as described hereinabove, the contrastbetween the intensity inside the iris and outside the iris, i.e. thehalo, in the image plane can be used for normalization or to obtain theeffective phase change value or the effective phase change area asdescribed hereinabove. The ratios between the intensities of the halo indifferent channels can be used as normalization factors of the differentintensity maps or different channels, as described hereinabove. Anotherpossible normalization methodology is to normalize the halo, orintensity of S, around the image for the different intensity maps. Thehalo around the image depends mainly on the object and spatial shape ofthe phase change, and does not depend on the phase change valueintroduced, and thus should be substantially identical in all intensitymaps.

Reference is now made to FIG. 10, which is a simplified schematicillustration of part of a wavefront analysis system using multiplechannels for different phase shifts in accordance with anotherembodiment of the present invention. As seen in FIG. 10, severaldifferent imaging channels 1002 are utilized for the same wavefront.These different imaging channels 1002 are obtained, preferably, bysplitting a beam from an illumination source 1003 using multiple beamsplitters 1004. The illumination is reflected from an object 1005. Ineach channel 1002, the wavefront undergoes a different phase shift,provided by multiple phase manipulators 1006. In this embodiment, all ofthe phase shifts can be performed substantially simultaneously. Eachintensity map is then obtained by a sensor 1010, such as a CCD camera,presented at each channel 1002. All channels 1002 use the sameillumination 1003 and the same primary optics 1001, but each may haveone or more additional lenses 1008. Using different channels 1002 fordifferent phase shifts it is possible to normalize the intensities ofall channels 1002 to compensate for the different optical components anddifferent optical paths of each channel 1002. One normalizationmethodology normalizes the integration of the intensity in the imageplane, so the sum over the entire field of view of all the intensitiesis equal. Another normalization method uses a non-coherent light sourcewhere no phase-delay is obtained and normalizes the intensity of thedifferent channels 1002.

Reference is now made to FIG. 11, which is a simplified schematicillustration of a system for analysis, detection and measurement ofmultilayer objects, constructed and operative in accordance with afurther preferred embodiment of the present invention.

The reflectivity of a multilayer material or object 1102 is dependent onthe wavelength of the reflecting light-source. The optical path lengthof each layer can be calculated by measuring the reflectivity indifferent wavelengths using a wideband light source 1104. Additionally,the thickness of each layer can be obtained if the refractive indices ofthe different materials are known. Current methods make no use of thephase of the reflected light, and the thickness at each location in thesample is measured according to the reflection from that location invarious wavelengths, independent of other locations. The wavefrontanalysis system of the present invention obtains and measures both theamplitude and the phase of the wavefront transmitted though or reflectedfrom an object. The amplitude measurement is used to obtain informationabout the object's transmittance or reflectance at the wavelength of theimpinging light and the phase measurement is used to obtain informationabout the object's optical quality or surface by using the wavefrontanalysis system, with a spectrally wideband light source, or a lightsource having several wavelengths. The reflectance of a multilayermaterial or object is obtained for different wavelengths. This is donesimilar to the wavefront analysis system described hereinabove withreference to FIGS. 1 and 2, where, for example a phase manipulator isinserted in the Fourier plane of an imaging system. In thisimplementation a spectrally wideband radiation source and a spectrallywideband sensor are used to obtain the intensity maps at the variouswavelengths of the radiation source, and subsequently obtain the phaseand amplitude of the reflected wavefront in each wavelength and in eachlocation in the object.

For each wavelength a different phase shift can be performed by a phasemanipulator 1108, such as a fixed optical-path change in a transparentplate, generating a different phase delay at each wavelength. Theoptical system may include additional optical elements such asbeam-splitter 1103 and lenses 1106 and 1110. The spectral images of theobject obtained in the image plane 1112 of the system are analyzed bymeans of an imaging spectrometer. An example of such an imagingspectrometer is described in U.S. Pat. No. 5,777,736. For eachwavelength, the amplitude and the phase of the wavefront reflected fromthe object 1102 are obtained. This is done in the various methodsdescribed hereinabove for the wavefront analysis method, such as byobtaining a plurality of intensity maps.

Once the reflected wavefronts are obtained, the optical path length ofeach layer is calculated, and, if the refractive indices of thedifferent materials are known, the thickness of each layer is obtained.Additionally, since the phase of the reflected wavefronts is alsoobtained, the three dimensional measurements of the surface of theobject can be extracted as well. Different materials can be detected bycomparing the reflection wavefronts obtained, to known and storedexpected reflection wavefronts of different materials.

In another embodiment, the wavefront analysis system is operative torecord the measurements while the polarization of the radiation sourceis changed. By measuring reflections from a multilayer material fordifferent wavelengths and different polarizations, the wavefrontanalysis system operates as a two-dimensional ellipsometer. In additionto conventional ellipsometery, additional phase information is obtained,which is utilized to extract the three dimensional measurements of theobject's surface.

The present invention also allows for a variety of methods to performdifferent phase changes. These different phase changes can be used, forexample, to yield the required differently phase changed transformedwavefronts. These methods include reflection or transmission modemethods, such as using different phase plates or a tunable spatial lightmodulator. Another method is to combine the reflection and transmissionmodes and use both in the same phase plate or spatial light modulator,to obtain more phase shifts from fewer phase plates. Another method isto use different wavelengths, which provide different effective phasechanges in each wavelength, and to include scaling of the Fouriertransform. Another example is a phase-changing spatial light modulatorin which the phase changing area surrounds the non-changing area,eliminating the need for excessive conductors. Still another method forcreating different phase changes is to use a moving phase plate whichhas different phase shifts at different locations. Yet another method isto use a reflective set of mirrors, where a moveable mirror is placedunder a mirror with a hole in its center. A further method is to usenonlinear material in the Fourier plane. Use of these methods is notlimited to phase manipulation of the wavefront analysis system, but alsomay be used to perform phase manipulation on any system.

Reference is now made to FIG. 12, which is a simplified schematicillustration of a wavefront analysis system using a combination ofreflection and transmission modes in phase shifts, constructed andoperative in accordance with another embodiment of the presentinvention. In the embodiment seen in FIG. 12, two mirrors and a beamsplitter 1202 are combined with a phase plate 1204, where the beam isdivided into 3 parts to 3 different channels. Channel 1 is not passingthrough or reflected from the phase plate. Channel 2 is reflected fromthe phase plate, and channel 3 is transmitted through the phase plate,Operation of the shutters enable images to be obtained in each of thechannels as appropriate, thus, when obtaining an image in channel 1,shutter 1 is in the open position and shutters 2 and 3 are closed, whileshutter. 2 is opened and shutters 1 and 3 are closed when obtaining animage in channel 2 and shutter 3 is opened and shutters 1 and 2 areclosed to obtain an image in channel 3. In each mode, transmission orreflection, a different phase shift is applied to the wavefront. Inchannel 1, no phase delay is applied. In the channel 3 transmission modethe phase delay is

${\phi = {\frac{2\pi}{\lambda}\left( {n - 1} \right)d}},$and in the channel 2 reflection mode the phase delay is

${\phi = {\frac{4\pi}{\lambda}d}},$where Φ is the phase delay, d is the depth or deposit height in thephase plate, λ is the wavelength and n is the index of refraction of thematerial of the phase plate. The ratio of the two phase delays is

$\frac{n - 1}{2}.$

Reference is now made to FIG. 13, which is a simplified schematicillustration of a wavefront analysis system using scaled phase plates inphase manipulations in accordance with still another preferredembodiment of the present invention. In this embodiment, multiple phasedelays are generated using a wavefront having different wavelengths,such as a light-source with different wavelengths, where the same phaseplate generates a different optical path change, or phase delay, foreach wavelength. However, in the position of the phase plate, such as inthe Fourier plane, the scaling of the diffraction pattern of eachwavelength is different. This results in each wavelength having adifferent ratio of the phase-changing area in the phase plate to theminimum spot size of the system. It is therefore desirable to rescalethe diffraction pattern of each wavelength so that the ratio will be thesame for all wavelengths. It is known in the art, that the opticalFourier transform of an object is obtained at the image plane of thelight source and that it is scaled according to the distances of thelight source and the object from the imaging lens. By modifying thedistances from the light sources of each wavelength to the object, theoptical Fourier transforms of the object from different wavelengths areobtained at different planes. The distances are chosen so that theoptical Fourier transforms are rescaled to obtain the same ratio for allwavelengths. When using only a single lens for the wavefront analysissystem, the object is imaged on the image plane, by the same lens thatcreates the Fourier transform in the Fourier plane.

Reference is now made to FIG. 14, which is a simplified schematicillustration of a tunable spatial light modulator with an active areasurrounding an inactive area, in accordance with yet another preferredembodiment of the present invention.

Another methodology for generating multiple phase delays is to createphase shifts of only the lower frequencies of the object in the Fourierplane, which are in the inner area of the Fourier plane. A tunablespatial light modulator positioned in the Fourier plane can providethese phase shifts. The spatial light modulator can consist of, forexample, a nematic liquid crystal, or LC, material, with a conductivelayer, or ITO, on an active area where different voltages are applied tothe conductive layer to cause different phase shifts in the liquidcrystal area adjacent to the conductive layer. However, to generatethese phase shifts in a generally central part of the liquid crystal,electrical conductors should pass through the outer non-active area toreach the conductive layer on the active area. These conductors cancause unwanted phase changes in the non-active area as well. In anotherembodiment of the present invention, which overcomes this problem, thephase shifts are performed on the higher frequencies in the outer areain the Fourier plane instead of the lower frequencies. Thus theconductive layer covers the outer area of the spatial light modulatorand there are no phase shifts in the inner area. There is thus no needfor electrical conductors in the inner area.

In certain applications, the actual phase change in each area is not themost important parameter but rather the relative phase change betweenthe inner and outer areas is the most important parameter. In thisembodiment, the same relative phase change can be provided either bychanging the phase, delays in the outer area in respect to a constantphase delay in the inner area or by changing the phase delays in theinner area in respect to a constant phase delay in the outer area.

Yet another method for creating different phase shifts or phasemanipulations is to use a mechanically movable phase plate which hasdifferent phase shifts at different locations. When a specific phasechange is required, the appropriate area of the movable phase plate isinserted in the optical path of the system.

Reference is now made to FIG. 15, which is a simplified schematicillustration of a spatial light modulator comprising two mirrors, inaccordance with yet another preferred embodiment of the presentinvention. As seen in FIG. 15, a reflective spatial light modulatorcomprises a moveable mirror 1502 placed under a mirror 1506 with a holein it. The movements of the movable mirror generate the different phaseshifts between different parts of a beam reflected from the two mirrormodule. The movable mirror is moved, for example, by a piezo-electricactuator 1508.

In accordance with still another preferred embodiment of the presentinvention, the different phase shifts or phase manipulations areproduced by means of a nonlinear material, preferably incorporated intoa filter in the Fourier plane. Since the refractive index of thisnonlinear material is dependent on the intensity of the radiationimpinging thereon, introducing it in the Fourier plane provides anothermethod for generating different phase shifts. When using objects withthe major part of the optical power in the Fourier plane concentrated inthe lower frequencies, mainly in the DC, the high intensity causes achange in the refractive index of the nonlinear material. This resultsin a change of the phase shift of the lower object frequencies.Different illumination intensities also cause different phase changes.The different intensity maps obtained thereby are then normalized andused to obtain the wavefront being analyzed in the wavefront analysissystem.

In yet a further embodiment, an absorber that can be saturated isintroduced in the Fourier plane. The absorption coefficient of thisabsorber is dependent on the intensity of the radiation impinging on it.Since the intensities of the lower frequencies are higher than in thehigher frequencies, a different transmission coefficient is obtained forthe lower and higher frequencies. Several measurements in differentintensities can be used to obtain the wavefront being analyzed in thewavefront analysis system.

The present invention also provides for improvements in common pathinterferometry. In common path interferometry microscopes, theinterfering object and reference beams propagate a similar path and havea small optical path difference. This provides several advantages,including enabling the use of non-perfect optical elements,insensitivity to vibrations and enabling the use of a broadband lightsource. There are several common path interferometry microscopes,including the Differential Phase Contrast, or DPC, microscope and theNomarski Differential Interference Contrast, or DIC, microscope.

The DPC microscope is a common path interferometer, where changes in theoptical path of the object are made visible and the three dimensionalstructure of a reflective object is reconstructed. In the DPCmicroscope, a split detector records the signal on either side of theoptical axis. Any local slope on the sample surface will shift theposition of the reflected beam on the detector. The difference betweenthe two signals indicates the steepness of the surface slope at thatpoint. By scanning, the surface can be reconstructed. In anotherembodiment, the phase difference between two adjacent points of theobject is measured. In a Michelson interferometer configuration, thebeam is split into two beams, the reference beam and the sample beam.The sample beam is then split again, using a Wolaston prism, into twocomponents with mutually perpendicular polarizations and focused on twoadjacent points on the object. The two reflected beams are then combinedand interfere with the reference beam. The phase difference between thetwo points can be calculated by the ratio of the interferenceintensities of the two polarizations.

The DIC microscope is a bright field microscope with apolarizer-analyzer pair and two prisms. The polarizer and the firstprism produce two wavefronts with fields polarized perpendicularly toeach other, which are translated with respect to each other. Bothwavefronts propagate through or are reflected by the object. Theanalyzer and the second prism, a Nomarski prism, recombine the twowavefronts and produce a fringe pattern of interference between the twowavefronts through which the phase map of the object is reconstructed.

Phase shift interferometry is a method where three or more phase shiftsare introduced between the interfering reference beam and the objectbeam. The phase shifts produce different interference patterns. Manyalgorithms for determination of the unknown wavefront have beenpublished. For three different measurements, of different phase delays,the phase and amplitude of the unknown wavefront at each location isexpressed as a function of the three measured intensity images and theother known parameters of the system. Each additional measurement, orphase delay function, increases the accuracy of the reconstruction ofthe wavefront when there are inaccuracies in intensity measurement or inthe known parameters, or when there are other noises or disturbances inthe system.

A one arm interferometer is an interferometer where the light propagatesthrough an optical fiber and is directed to the object's surface. Aportion of the light is reflected by the fiber end and serves as thereference beam while another portion is reflected by the object'ssurface and serves as the object beam. The two beams interfere and thephase difference can be calculated.

Current methodologies for optical disk data storage are based on storingthe data bits as pits on the disk's surface. By focusing light on thedisk's surface, a destructive or instructive interference between thelight reflected by the pit and the light reflected by the pit'ssurrounding area, the land, are obtained. There are several methods forincreasing the available data storage on an optical disk. One method isto utilize multiple layers, where each layer serves as a differentoptical disk. The disk is read using, a single wavelength ormulti-wavelength beam focused on a specific layer or multiple layerssimultaneously. Another reading and storage method, the “Color OpticalMemory”, increases the available data storage by utilizing differentcolors, using white light and a thin film. The data is stored in a thinlayer on the disk's surface with locally different thicknesses.Different wavelengths are reflected differently by the thin film, sothat different thicknesses of the thin film correspond to differentcolor light reflected. The present invention provides for improvementsof the interferometry and microscopy methods described hereinabove invarious methods and embodiments described below.

Reference is now made to FIG. 16, which is a simplified schematicillustration of an implementation of an improved common path Michelsoninterferometer, in accordance with one embodiment of the presentinvention. The incoming laser beam from laser 1600 is split by the beamsplitter 1602 into two beams 1604 and 1606. Beam 1604 is focused bymeans of an optical system (not shown) on a point, or sub-surface, onthe surface of an object 1608, while beam 1606 is focused, by means ofan optical system including a mirror 1607, on an adjacent point, orsub-surface, of object 1608. After reflection, the two beams arerecombined and produce an interference pattern on detector 1610, such asa CCD camera or other electronic imaging device. A tunable phase delay,produced by a tunable optical element 1612, such as spatial lightmodulator or other suitable device, is introduced in the optical path ofbeam 1606. The tunable optical element results in different phase delaysbetween beams 1604 and 1606, creating different interference patterns.From three different interference patterns of different phase delays,the phase and the amplitude differences of both points, or sub-surfaces,can be calculated. This embodiment provides the advantages of the commonpath interferometry and the advantages of phase shift interferometry.Additionally, this embodiment is also applicable using white light ordifferent wavelengths. Alternatively, a static phase plate can be usedinstead of the tunable optical element 1612, utilizing differentwavelengths in the illumination source 1600.

In another embodiment, the beam is split into two components withmutually perpendicular polarizations as in the DPC describedhereinabove, where the phase delay is introduced to one polarizationcomponent.

In still another embodiment, the Michelson interferometer is actualizedusing fiber optics. The beam propagates through an optical fiber, isthen split by a 50:50 coupler into two fibers and directed to twoadjacent points on the sample's surface. The phase delay is thenintroduced into one arm of the interferometer by any conventional phasedelay device.

In a further embodiment, different wavelengths are directed to the twofibers by means of wavelength division multiplexing resulting indifferent phase delays. Additionally, a bundle of fibers may be utilizedto provide a system for two-dimensional measurements.

In another embodiment, the present invention can be used to enable thedifferential phase contrast interferometer described hereinabove to scantwo-dimensional objects, where the local slope and phase are calculated,using two or more adjacent pixels in the camera. Additionally, a tunablephase delay device can be introduced to one side of the optical axis toproduce different phase delays between the two sides, also providing theadvantages of the phase shift method.

In yet another embodiment, two or more wavelengths are used to producethe different phase shifts between both sides of the optical axis.

Reference is now made to FIG. 17, which is a simplified illustration oflight reflecting from a disk being scanned in accordance with yetanother preferred embodiment of the present invention. In thisembodiment, the differential phase contrast interferometer is used withwhite light to increase the available data storage. Data bits are storedon the surface of an optical disk 1700 by applying pits 1702, wheredifferent depths represent different data. The white light is focused bymeans of a conventional optical system on a point on the disk's surface.As seen in FIG. 17, part of the white light 1704 is reflected by the pitand the other part 1706 is reflected by the land 1710. As indifferential phase contrast interferometry, both parts of light combineand interfere. Thus, different wavelengths have reconstructive anddestructive interference for different depths, and the light isreflected from the disk's surface in different colors.

In another embodiment, the refractive index on the disk's surface ischanged locally to emulate the pit and the land, instead of utilizingactual pits.

In yet another embodiment of the present invention, two or morewavelengths are directed through the fiber by means of wavelengthdivision multiplexing introducing different phase shifts for eachwavelength. This provides different interferences for each wavelengthand realizes the advantages of the phase shift method. Alternatively,the fiber end is suitably coated to transmit one wavelength and reflectthe other. By scanning the object's surface, the two different reflectedwavelengths interfere and the phase is detected in the sense of theHeterodyne detection.

Reference is now made to FIG. 18, which is a simplified schematicillustration of a wavefront analysis method and system using a singleintensity map, and to FIG. 19, which is a simplified illustration of anillumination pattern obtained therefrom in the image plane, inaccordance with another preferred embodiment of the present invention.

In holography, two light beams, a reference beam and an object beam,interfere on a film to provide the fringes that are recorded on thefilm. The original object beam is reconstructed by illuminating the filmwith a reconstruction beam identical to the reference beam. Theinterference pattern on the film is given by equation 18.1, where U andV are the complex amplitudes of the reference and the object beamrespectively.I=|U+V| ² =|U| ² +|V| ² +UV*+U*V  (18.1)The opacity of the film is proportional to the illumination intensity ofthe image recorded on it. After illuminating the film with thereconstruction beam identical to the reference beam, the complexamplitude transmitted through the film is stated in equation 18.2.UI=(|U| ² +|V| ²)U+U ² V*+|U| ² V  (18.2)The first term in equation 18.2 describes a beam that propagates in thedirection of the reference beam. The second term describes a beam thatpropagates in a direction which is the conjugate direction of theobject's beam with an additional rotation. The final tern describes areconstruction of the object beam. The original object beam can bereconstructed electronically by multiplying the intensity pattern bymeans of a computer with a virtual reconstruction beam. Afterpropagating forward the three beams, the first two beams can be filteredout. A reverse propagation reconstructs the object's beam.

In the current embodiment, an imaging system is used, where phase changeis applied to the transformed wavefront, similarly to the wavefrontanalysis system described hereinabove with reference to FIG. 1 and FIG.2, the intensity map in the image plane is given by equation 18.3, whereS, which is generally related to the light diffracted by the Fourierfilter, was described hereinabove in FIG. 3.I=|Ae ^(φ)+(e ^(iθ)−1)S| ² =|V+U| ²  (18.3)

In this representation where V represents Ae^(φ) and U represents(e^(iθ)−1)S, the phase change of the transformed wavefront can also beconsidered as a hologram of two interfering wavefronts, the object beamdenoted by V and the “S-beam” denoted by U, as seen in FIG. 18. If theobject plane is limited by an iris, the imaging system images theobject, generating the object's image 1900, limited by the iris image1902, in the image plane. As a result, the amplitude of S can bereconstructed by the halo 1904 around the iris image 1902 using themethod described hereinabove. The object beam can be reconstructed byelectronically multiplying the intensity image measured with thereference beam, which is the S beam. The system thus requires only asingle intensity map. FIG. 19 is an illustration of an illuminationpattern in the image plane generated using an iris as describedhereinabove.

Reference is now made to FIG. 20, which is a simplified partiallyschematic, partially pictorial illustration of a system for surfacemapping, employing the functionality and structure of FIGS. 1 and 2. Asseen in FIG. 20, a beam of radiation, such as light or acoustic energy,is supplied from a radiation source 2000, optionally via a beam expander2002, onto a beam splitter 2004, which reflects at least part of theradiation onto a surface 2006 to be inspected. The radiation reflectedfrom the inspected surface 2006 is a surface mapping wavefront, whichhas an amplitude and a phase, and which contains information about thesurface 2006. At least part of the radiation incident on surface 2006 isreflected from the surface 2006 and transmitted via the beam splitter2004 and focused via a focusing lens 2008 onto a phase manipulator 2010,such as a spatial light modulator or a series of different transparent,spatially non-uniform objects, which is preferably located at the imageplane of radiation source 2000. A second lens 2012 is arranged so as toimage surface 2006 onto a detector 2014, such as a CCD detector.Preferably the second lens 2012 is arranged such that the detector 2014lies in its focal plane. The output of detector 2014, an example ofwhich is a set of intensity maps designated by reference numeral 2015,is preferably supplied to data storage and processing circuitry 2016,which preferably carries out the third sub-functionality describedhereinabove with reference to FIG. 1, providing an output indicating atleast one and possibly both of the phase and the amplitude of thesurface mapping wavefront. This output is preferably further processedto obtain information about the surface 2006, such as geometricalvariations and reflectivity of the surface. In accordance with apreferred embodiment of the illustrated embodiment, the phasemanipulator 2010 applies a plurality of different spatial phase changesto the radiation wavefront reflected from surface 2006 and Fouriertransformed by lens 2008. Application of the plurality of differentspatial phase changes provides a plurality of differently phase changedtransformed wavefronts which are subsequently detected by detector 2014.

Reference is now made to FIG. 21, which is a simplified partiallyschematic, partially pictorial illustration of a system for objectinspection, employing the functionality and structure of FIGS. 1 and 2.As seen in FIG. 21, a beam of radiation, such as light or acousticenergy, is supplied from a radiation source 2100, optionally via a beamexpander, onto at least partially transparent object to be inspected2102. The radiation transmitted through the inspected object 2102 is anobject inspection wavefront, which has an amplitude and a phase, andwhich contains information about the object 2102. At least part of theradiation transmitted through object 2102 is focused via a focusing lens2104 onto a phase manipulator 2106, such as a spatial light modulator ora series of different transparent, spatially non-uniform objects, whichis preferably located at the image plane of radiation source 2100. It isappreciated that phase manipulator 2106 can be configured such that asubstantial part of the radiation focused thereonto is reflectedtherefrom. Alternatively the phase manipulator 2106 can be configuredsuch that a substantial part of the radiation focused thereonto istransmitted therethrough. A second lens 2108 is arranged so as to imageobject 2102 onto a detector 2110, such as a CCD detector. Preferably,the second lens 2108 is arranged such that the detector 2110 lies in itsfocal plane. The output of detector 2110, an example of which is a setof intensity maps designated by reference numeral 2112, is preferablysupplied to data storage and processing circuitry 2114, which preferablycarries out the third sub-functionality described hereinabove withreference to FIG. 1, providing an output indicating at least one andpossibly both of the phase and the amplitude of the object inspectionwavefront. This output is preferably further processed to obtaininformation about the object 2102, such as a mapping of the object'sthickness, refractive index or transmission.

Reference is now made to FIG. 22, which is a simplified partiallyschematic, partially pictorial illustration of a system for spectralanalysis, employing the functionality and structure of FIGS. 1 and 2. Asseen in FIG. 22, a beam of radiation, such as light or acoustic energy,is supplied from a radiation source to be tested 2200, optionally via abeam expander, onto a known element 2202, such as an Etalon or aplurality of Etalons. Element 2202 is intended to generate an inputwavefront, having at least varying phase or intensity. The radiationtransmitted through the element 2202 is a spectral analysis wavefront,which has an amplitude and a phase, and which contains information aboutthe spectrum of the radiation source 2200. At least part of theradiation transmitted through element 2202 is focused via a focusinglens 2204 onto a phase manipulator 2206, such as a spatial lightmodulator or a series of different transparent, spatially non-uniformobjects, which is preferably located at the image plane of radiationsource 2200. It is appreciated that phase manipulator 2206 can beconfigured such that a substantial part of the radiation focusedthereonto is reflected therefrom. Alternatively the phase manipulator2206 can be configured such that a substantial part of the radiationfocused thereonto is transmitted therethrough. A second lens 2208 isarranged so as to image element 2202 onto a detector 2210, such as a CCDdetector. Preferably, the second lens 2208 is arranged such that thedetector 2210 lies in its focal plane. The output of detector 2210, anexample of which is a set of intensity maps designated by referencenumeral 2212, is preferably supplied to data storage and processingcircuitry 2214, which preferably carries out the third sub-functionalitydescribed hereinabove with reference to FIG. 1, providing an outputindicating at least one and possibly both of the phase and the amplitudeof the spectral analysis wavefront. This output is preferably furtherprocessed to obtain information about the radiation source 2200, such asthe spectrum of the radiation supplied from radiation source 2200.

Reference is now made to FIG. 23, which is a simplified illustration ofcombining a wavefront-analysis system and an optical imaging system inaccordance with yet another preferred embodiment of the presentinvention.

As described hereinabove, a variety of wavefront analysis methods exist,analyzing wavefronts reflected from or transmitted through an object,such as interferometry, and the wavefront analysis methods describedhereinabove. The present invention, provides embodiments to combinethese wavefront analysis methods with a variety of imaging methods andapparatuses, such as optical microscopes. Combining these twofunctionalities, such that a wavefront to be analyzed is imaged throughthe imaging system, and subsequently analyzed by a wavefront analysisfunctionality, allows wavefront analysis of the imaged object ratherthan the original object. The imaged object has several identicalfeatures to the original object, but some differences, such as differentmagnification, that facilitate the wavefront analysis. The wavefrontanalysis is thus performed on an image of the object to be inspected,where the image, and thus the wavefront to be analyzed, is obtained bythe imaging system, such as a microscope or another imaging system. Theimage wavefront, which is the wavefront that is analyzed afterpropagation through the imaging system, is related to the originalwavefront, and thus applying the wavefront analysis functionality to theimage wavefront provides information about the original wavefront. Thecombination of the imaging and wavefront analysis functionalities can beperformed based on any conventional wavefront analysis method and anyconventional imaging system.

As seen in FIG. 23, this embodiment of the present invention includestwo functionalities, an imaging functionality and an image wavefrontanalysis functionality. A wavefront to be analyzed 2310 is imaged by theimaging functionality 2320 resulting in an image wavefront 2330. Theimage wavefront 2330 is analyzed by an image wavefront analysisfunctionality 2340, and the resulting information about the wavefront issubsequently processed and stored, by a data storage and processingcomponent 2350. It is noted that imaging functionality 2320 and imagewavefront analysis functionality 2340 may be embodied in an integratedsystem, where the image wavefront 2330 is generated internally withinthe system.

The wavefront to be analyzed 2310 can be any suitable wavefront, such asa wavefront reflected from an object to be inspected, a wavefronttransmitted through an object to be inspected, or a wavefront impingingon a known object from a radiation source to be spectrally analyzed. Theimaging functionality 2320 and the image wavefront analysisfunctionality 2340 may be independent, both in hardware and inperformance. Thus, various conventional imaging systems can be used forthe imaging functionality 2320. Additionally, various wavefront analysissystems can be used for the image wavefront analysis functionality 2340,where the image wavefront analysis functionality 2340 provides aquantitative wavefront analysis of the image wavefront 2330 obtained bythe imaging functionality 2320.

In another embodiment of the present invention, the interface betweenthe imaging functionality 2320 and the wavefront analysis functionality2340 is identical to the interface between an imaging system and a CCDcamera. Furthermore, the wavefront analysis module may be identical insize, mechanical interfaces, optical interfaces, functionality and form,to a CCD camera.

In accordance with still another preferred embodiment of the presentinvention, the intermediate image obtained by the imaging functionality2320 at the image plane, serves as an “object” for the image wavefrontanalysis functionality 2340. This image plane contains the imagewavefront 2330, which is subsequently analyzed by the image wavefrontanalysis functionality 2340. It should be noted that according to thepresent invention, the image wavefront analysis functionality 2340 canbe operated in any plane of the imaging functionality and need notnecessarily operate on the image plane.

In accordance with yet another embodiment of the present invention theimaging functionality 2320 and the image wavefront analysisfunctionality 2340 are combined by incorporating a wavefront analysissystem into any existing imaging system, in particular, an opticalimaging system such as an optical microscope. In this embodiment, thewavefront emerging from the existing optical system is the imagewavefront 2330, which is subsequently analyzed by the image wavefrontanalysis functionality 2340. This embodiment enables transformingexisting imaging systems into wavefront analysis systems.

In accordance with another preferred embodiment of the presentinvention, the imaging functionality 2320 is realized by a microscope,and the image wavefront 2330 is the wavefront imaged by the microscope.Alternatively, the imaging functionality 2320 is realized by any otheroptical system, such as a simple lens or a telescope.

In accordance with a further preferred embodiment of the presentinvention, image wavefront analysis functionality 2340 is realized bythe wavefront analysis system described hereinabove with reference toFIGS. 1 and 2 and as detailed in PCT Application No. PCT/IL/01/00335,and in U.S. Provisional Patent Applications, Ser. Nos. 60/351,753 and60/406,593, of the present assignee, the disclosures of which are herebyincorporated by reference. Alternatively, the image wavefront analysisfunctionality 2340 is realized by any conventional wavefront analysismethod, such as white light interferometry, phase shift interferometry,phase-contrast, DIC, spectral measurements, polarization measurementsand Shack-Hartman.

In accordance with another embodiment of the present invention, theimage wavefront analysis functionality 2340 is realized by manipulatingthe phase, amplitude and/or polarization of part of the image wavefront2330, after propagating the image wavefront to a certain plane.Alternatively, the image wavefront analysis functionality 2340 isrealized by manipulating the phase, amplitude and/or polarization ofpart of the image wavefront 2330 at the image plane of imagingfunctionality 2320, before propagating the image wavefront to anotherplane.

The wavefront analysis system of the present invention may be appliedfor various usages, such as object inspection, i.e. analyzing thewavefront impinging on an object to be inspected, intensity retrieval,phase retrieval, polarization retrieval and/or spectral analysis.

In accordance with a preferred embodiment of the present invention, theintermediate image is generated by a microscope using a variety ofobjectives which may be switched or interchanged without affecting thefunctionality of the wavefront analysis module. These objectives may beany suitable objectives, such as commercial objectives, custom designedobjectives, etc. Additionally, the intermediate image generated by themicroscope using a variety of objectives may have a variety of opticalparameters including various magnifications, working distances, exitpupil locations and numerical apertures.

In accordance with another preferred embodiment of the presentinvention, the imaging functionality 2320 may generate the imagewavefront 2330 by using a variety of objectives or lenses, which may beswitched or interchanged without affecting the image wavefrontfunctionality 2340. The objectives or lenses may be any suitableobjectives or lenses such as commercial objectives or lenses, customdesigned objectives or lenses, etc. Additionally, the imagingfunctionality 2320 may have a variety of optical parameters includingvarious magnifications, working distances, exit pupil locations andnumerical apertures.

In accordance with yet another embodiment of the present invention, theimaging functionality 2320 that generates the image wavefront 2330includes additional optical elements in the main optical branch thatprovide an optical alignment function. Alternatively, the additionaloptical elements are provided in an additional optical branch.

In accordance with a preferred embodiment of the present invention, thewavefront analysis system includes a light source. Preferably, the lightsource is monochromatic with high temporal coherence. Alternatively, thelight-source is a partially coherent or non-coherent light source withone or more wavelengths.

In accordance with another preferred embodiment of the presentinvention, the wavefront analysis system includes an illuminationmodule. Preferably, the illumination module is generated by a highlyspatial coherent light source such as a point light source or parallelillumination. Alternatively, the illumination is generated by a lightsource with another spatial shape, such as a line or more than onepoint, with lower spatial coherence.

In accordance with still another preferred embodiment of the presentinvention, the image wavefront 2330 is the wavefront of the imageobtained by the imaging functionality in the image plane. Alternatively,the image wavefront 2330 is the wavefront obtained in an arbitraryoptical plane of the imaging functionality. Additionally, the imagewavefront 2330 can be propagated to any other desired plane, using knownformulas, and subsequently analyzed by the image wavefront analysisfunctionality 2340. Alternatively, the image wavefront analysisfunctionality 2340 includes a sub-functionality that propagates theimage wavefront to any other desired plane, using known formulas, andsubsequently analyzes the propagated wavefront.

Reference is now made to FIG. 24, which includes a general block diagramof the components of a preferred embodiment of a wavefront analysismodule performing the image wavefront analysis functionality 2340. Asseen in FIG. 24, the illumination module consists of two different lightsources 2402 with two different wavelengths. The illuminations from thetwo light sources are combined by a beam combiner 2404 or otherconventional device and are collimated by a collimator 2406. Thecollimated beam is reflected or transmitted by a beam splitter 2408 intoan imaging system 2410, such as a microscope, through the image plane2412 and propagated through the components of the imaging system 2410 toilluminate an object to be inspected 2414. The reflected light from theobject constitutes the wavefront to be analyzed. This wavefront, afterpropagating through the imaging system 2410, forms an image of theobject in the microscope's image plane 2412. This imaging system 2410 isequivalent to imaging functionality 2320 of FIG. 23. The image wavefrontserves as an object for the image wavefront analysis module 2416 and isanalyzed by the wavefront analysis module, including obtaining intensitymaps by a camera, and analyzing the intensity maps by an electronicssystem and a computation system.

In accordance with yet another embodiment of the present invention, thewavefront measurement methods and systems described hereinabove may beincorporated into existing imaging systems and methods. In thisembodiment, light is transmitted through or reflected from an object tobe inspected, and an image of the object to be inspected, and thewavefront to be analyzed, is obtained by an optical system, such as amicroscope or another imaging system. This is achieved by incorporatingthe wavefront analysis system into any existing optical system, or inthe design of an optical system, in particular an imaging system. Thewavefront emerging from the existing optical system is then analyzed bythe wavefront analysis system.

In one example of the above, the wavefront analysis system isincorporated, as an add-on module, to an existing microscope, such as amicroscope imaging objects by reflecting light, a microscopetransmitting light through an inspected object or a microscope providingboth transmission and reflection. The phase changes of the wavefrontanalysis system are performed to the transformed wavefronts emergingfrom the microscope. The magnification of the wavefront analysis systemcan be times one magnification, 1×, or any other magnification, wherethe overall magnification of the combined microscope and wavefrontanalysis system is the product of the magnification of the wavefrontanalysis system and the magnification of the microscope. In thisembodiment, only a single magnification of the wavefront analysis systemis required, and different overall magnifications, resulting indifferent fields of view and different lateral resolutions, can beobtained by switching the magnifications of the microscope, for example,by changing objective lenses. The interface between the wavefrontanalysis system and the microscope is similar to the interface of a CCDcamera and the microscope, where the wavefront to be analyzed is thewavefront related to the ‘image’ of the original object that would be inthe image plane of the CCD camera. If an iris is used to block an areaof the inspected object, it is placed in the image plane, where theimage of the object is obtained by the microscope. Additionally, anillumination system can be incorporated into the wavefront analysissystem, where the illumination light passes through the microscope,reflects from the inspected object back through the microscope and intothe wavefront analysis system. In another embodiment a separateillumination system, or the illumination system of the microscope, isused to reflect light from the object or transmit light through it andthus generate the original wavefront that is imaged and analyzed.

In a further embodiment, the module performing the phase manipulations,such as a spatial light modulator, can be inserted into an existingmicroscope or other imaging device, in various locations, such as in theFourier plane of the imaging objective, using the original opticalcomponents of the existing optical systems.

In any of the above implementations, the light source can be theoriginal light source of the existing optical systems, used with orwithout modifications, or a dedicated light source added to the system.

The wavefront analysis system is an imaging system, where intensityimages of the phase changed transformed wavefronts of the object areobtained, for example by a camera. These intensity images are utilizedto reconstruct the wavefront. Since the wavefront analysis system is animaging system, it can be adjusted to obtain a focused imagine at avariety of distances to the object. Therefore, the wavefront analysissystem can also be used for analyzing wavefronts of distant objects.

Reference is now made to FIG. 25, which is a simplified partiallyschematic, partially block diagram illustration of a wavefront analysissystem including an imaging functionality and a phase manipulated basedimage wavefront analysis functionality of the type described withreference to FIG. 23. As seen in FIG. 25, an enhanced wavefront analysissystem includes an imaging functionality and an image wavefront analysisfunctionality. The wavefront to be analyzed 2510 is imaged by theimaging functionality 2520 resulting in an image wavefront 2530. Theimage wavefront 2530 is analyzed by an image wavefront analysisfunctionality 2540, and the resulting information about the imagewavefront 2530 is subsequently processed and stored by the data storageand processing component 2550. It is noted that imaging functionality2520 and image wavefront analysis functionality 2540 may be embodied asan integrated system, where the image wavefront 2530 is generatedinternally. A different scale and magnification may be obtained byimaging the wavefront to be analyzed 2510 through imaging system 2520.

As seen in FIG. 25, image wavefront analysis functionality 2540 includesfocusing image wavefront 2530, preferably using a lens 2542, onto amanipulator 2544, which is preferably located at the focal plane of lens2542. The manipulator 2544, such as a spatial light modulator or aseries of different transparent, spatially non-uniform objects,generates an optical manipulation, such as a phase change. A second lens2546 is arranged to image the image wavefront 2530 onto a detector 2548,such as a CCD detector. The wavefront to be analyzed 2510 is thusre-imaged onto detector 2548. Preferably, the second lens 2546 isarranged such that the detector 2548 lies in the imaging plane of theimage wavefront 2530.

The wavefront to be analyzed 2510 can be any suitable wavefront, such asa wavefront reflected from an object to be inspected, a wavefronttransmitted through an object to be inspected, or a wavefront impingingon a known object from a radiation source to be spectrally analyzed. Theimaging functionality 2520 and the image wavefront analysisfunctionality 2540 may be independent of one another, both in hardwareand in performance. Thus various conventional imaging systems can beused for the imaging functionality 2520.

In another embodiment of the present invention, the interface betweenthe imaging functionality 2520 and the image wavefront analysisfunctionality 2540 is identical to the interface between an imagingsystem and a CCD camera. Furthermore, the wavefront analysis module canbe identical in size, mechanical interfaces, optical interfaces,functionality and form to a CCD camera.

In accordance with still another preferred embodiment of the presentinvention, an intermediate image, obtained by the imaging functionality2520 at its image plane, serves as an “object” for the image wavefrontanalysis functionality 2540. This image plane contains the imagewavefront 2530, which is subsequently analyzed by the image wavefrontanalysis functionality 2540. It should be noted that according to thepresent invention, the image wavefront analysis functionality 2540 canbe operated in any plane of the imaging functionality and need notnecessarily operate on the image plane.

In accordance with another embodiment of the present invention theimaging functionality 2520 and the image wavefront analysisfunctionality 2540 are combined by incorporating a wavefront analysissystem into any existing imaging system, in particular, an opticalimaging system such as an optical microscope. In this embodiment, thewavefront emerging from the existing optical system is the imagewavefront, which is subsequently analyzed by the image wavefrontanalysis functionality 2540. This embodiment enables transformingexisting imaging systems into wavefront analysis systems.

In accordance with yet another embodiment of the present invention, themanipulator 2544 is located at the effective focal plane of the combinedoptics contained in the imaging functionality 2520 and lens 2542.

In accordance still another embodiment of the present invention, thewavefront analysis functionality 2540 analyzing the image wavefront 2530obtained by the imaging functionality 2520 is implemented by anywavefront analysis method or apparatus described in PCT Application No.PCT/IL/01/00335 or any wavefront analysis method or apparatus describedin U.S. Provisional Patent Applications, Ser. Nos. 60/351,753 and60/406,593, of the present assignee.

In accordance with another preferred embodiment of the presentinvention, the image wavefront analysis functionality 2540 analyzing theimage wavefront 2530 obtained by the optical system 2520 is implementedby any wavefront analysis method or apparatus which is accomplished bymanipulating the phase, amplitude and/or polarization of part of theimage wavefront 2530. This manipulation of the phase, amplitude and/orpolarization may be performed in the image plane of the imaging systembefore propagating the image wavefront to another plane or afterpropagating the wavefront to a desired plane.

In accordance with yet another preferred embodiment of the presentinvention, the imaging functionality 2520 is realized by a microscope,and the image wavefront 2530 is the wavefront imaged by the microscope.Alternatively, the imaging functionality 2520 is realized by any otheroptical system, such as a simple lens or a telescope.

In accordance with a further preferred embodiment of the presentinvention, the intermediate image is generated by the imaging system2520 by using a variety of objectives where the various objectives maybe switched or interchanged without affecting the functionality of theimage wavefront analysis module 2540. The objectives may be any suitableobjectives such as commercial objectives, custom designed objectives,etc. Additionally, the intermediate image generated by the imagingsystem 2520 using a variety of objectives, may have a variety of opticalparameters including various magnifications, working distances, exitpupil locations and numerical apertures.

In accordance with a preferred embodiment of the present invention, theimage wavefront 2530 is the wavefront of the image obtained by theimaging functionality in the image plane. Alternatively, the imagewavefront 2530 is the wavefront obtained in an arbitrary optical planeof the imaging functionality. Additionally, the image wavefront 2530 canbe propagated to any other desired plane, using known formulas, andsubsequently analyzed by the image wavefront analysis functionality2540. Alternatively, the image wavefront analysis functionality 2540includes a sub-functionality that propagates the image wavefront to anyother desired plane using known formulas, and subsequently analyzes thepropagated wavefront.

The imaging functionality 2520 that generates the image wavefront 2530preferably includes a light source. The light source may be amonochromatic light source with high temporal coherence or a partial ornon coherent light source with one or more wavelengths. The illuminationmay be generated by a light source providing high spatial coherence suchas a point light source or parallel illumination, or with light sourcesof other spatial shapes with lower spatial coherence, such as a linelight source or a multipoint light source.

In accordance with yet another embodiment of the present invention, anywavefront analysis method or apparatus described in PCT Application No.PCT/IL/01/00335 or in U.S. Provisional Patent Applications, Ser. Nos.60/351,753 or 60/406,593, of the present assignee, may be applied at animage plane of an object to be inspected, and thus operate on an imagewavefront.

Reference is now made to FIG. 26, which is a simplified partiallyschematic, partially block diagram illustration of a wavefront analysissystem operating on an image wavefront. This embodiment providesenhanced methods and apparatus for wavefront analysis, 3D measurementand spectral analysis, based on analyzing an image wavefront.

As seen in FIG. 26, an image wavefront 2650, which can be obtained suchas by imaging a wavefront through an imaging system, is focused by alens 2652, onto a manipulator 2654, such as a spatial light modulator ora series of different transparent, spatially non-uniform objects,preferably located at the focal plane of lens 2652, which generatesoptical manipulations such as phase changes. A second lens 2656 isarranged so as to image wavefront 2650 onto a detector 2658, such as aCCD detector. Preferably the second lens 2656 is arranged such that thedetector 2658 lies in its focal plane. The output of detector 2658 ispreferably supplied to data storage and processing circuitry 2660.Analyzing an image wavefront allows the wavefront analysis module to belocated at a more convenient location rather than in proximity to theoriginal object being analyzed.

Preferably, the wavefront analysis system of FIG. 26 is combined intoany existing imaging system, in particular, an optical imaging systemsuch as an optical microscope. In this embodiment, the wavefrontemerging from the existing optical system is the image wavefront 2650,which is subsequently analyzed by a wavefront analysis system. Thisembodiment enables transforming existing imaging systems into wavefrontanalysis systems.

The image wavefront 2650 can be any suitable image wavefront, such as awavefront reflected from an object to be inspected, a wavefronttransmitted through an object to be inspected, or a wavefront impingingon a known object from a radiation source to be spectrally analyzed. Theimage wavefront analysis functionality can be completely independent ofthe wavefront origination and on the nature of the imaging. Variousconventional imaging systems can be used to generate the image wavefront2650.

In accordance with a preferred embodiment of the present invention, theimage wavefront 2650 serves as an “object” for the image wavefrontanalysis functionality. The image wavefront 2650 is subsequentlyanalyzed by the image wavefront analysis functionality. It should benoted that the image wavefront can be at any plane of an imagingfunctionality and not necessarily be on the image plane.

Reference is now made to FIG. 27, which is a simplified partiallyschematic, partially pictorial illustration of a system for surfacemapping, employing the functionality and structure of FIG. 25. As seenin FIG. 27, a beam of radiation, such as light or acoustic energy, issupplied from a radiation source 2700, optionally via a beam expander2702, onto a beam splitter 2704, which reflects at least part of theradiation through the imaging system image plane 2730 and through theimaging system 2722 onto a surface of an object 2720 to be inspected.The radiation reflected from the inspected surface 2720 is a surfacemapping wavefront, which has an amplitude and a phase, and whichcontains information about the surface 2720. The imaging system 2722produces an image 2706 of the object 2720 in the image plane 2730. Theimage plain 2730 contains an image surface mapping wavefront, which hasan amplitude and a phase, and which contains information about thesurface 2720. At least part of the radiation propagrating from the imageplane 2730 is transmitted via the beam splitter 2704 and focused via afocusing lens 2708 onto a phase manipulator 2710, such as a spatiallight modulator or a series of different transparent, spatiallynon-uniform objects, which is preferably located at the image plane ofradiation source 2700. A second lens 2712 is arranged so as to image theimage plane 2730 onto a detector 2714, such as a CCD detector.Preferably the second lens 2712 is arranged such that the detector 2714lies in its focal plane. The output of detector 2714, an example ofwhich is a set of intensity maps designated by reference numeral 2715,is preferably supplied to data storage and processing circuitry 2716,which preferably carries out the third sub-functionality describedhereinabove with reference to FIG. 1, providing an output indicating atleast one and possibly both of the phase and the amplitude of the imagesurface mapping wavefront. This output is preferably further processedto obtain the phase and the amplitude of the surface mapping wavefrontand thus information about the object 2720, such as geometricalvariations and reflectivity of the surface. In accordance with apreferred embodiment of the mentioned invention, the phase manipulator2710 applies a plurality of different spatial phase changes to theradiation wavefront propagates from surface 2720 and Fourier transformedby lens 2708. Application of the plurality of different spatial phasechanges provides a plurality of differently phase changed transformedwavefronts which may be subsequently detected by detector 2714.

Reference is now made to FIG. 28, which is a simplified partiallyschematic, partially pictorial illustration of a system for objectinspection employing the functionality and structure of FIG. 25. As seenin FIG. 28, a beam of radiation, such as light or acoustic energy, issupplied from a radiation source 2800, optionally via a beam expander,onto at least partially transparent object to be inspected 2802. Theradiation transmitted through the inspected object 2802 is an objectinspection wavefront, which has an amplitude and a phase, and whichcontains information about the object 2802. At least part of theradiation transmitted through object 2802 is transmitted through theimaging system 2820 and the object's image is obtained in an image plane2830 of the imaging system. The wavefront image plane 2830 contains animage object inspection wavefront 2840, which has an amplitude and aphase, and which contains information about the object 2802. Theradiation propagated through the image plane 2830 is focused via afocusing lens 2804 onto a phase manipulator 2806, such as a spatiallight modulator or a series of different transparent, spatiallynon-uniform objects, which is preferably located at the image plane ofradiation source 2800. It is appreciated that phase manipulator 2806 canbe configured such that a substantial part of the radiation focusedthereonto is reflected therefrom. Alternatively the phase manipulator2806 can be configured such that a substantial part of the radiationfocused thereonto is transmitted therethrough. A second lens 2808 isarranged so as to image the image plane 2830 onto a detector 2810, suchas a CCD detector. Preferably, the second lens 2808 is arranged suchthat the detector 2810 lies in its focal plane. The output of detector2810, an example of which is a set of intensity maps designated byreference numeral 2812, is preferably supplied to data storage andprocessing circuitry 2814, which preferably carries out the thirdsub-functionality described hereinabove with reference to FIG. 1,providing an output indicating at least one and possibly both of thephase and the amplitude of the image object inspection wavefront 2840.This output is preferably further processed to obtain the phase andamplitude of the surface mapping wavefront and thus information aboutthe object 2802, such as a mapping of the object's thickness, refractiveindex or transmission.

Reference is now made to FIG. 29, which is a simplified partiallyschematic, partially pictorial illustration of a system for spectralanalysis employing the functionality and structure of FIG. 25. As seenin FIG. 29, a beam of radiation, such as light or acoustic energy, issupplied from a radiation source to be tested 2900. The radiationpropagates through a known element 2902, such as an Etalon or aplurality of Etalons. Element 2902 is intended to generate an inputwavefront, having at least varying phase or intensity. The radiationtransmitted through the element 2902 is a spectral analysis wavefront,which has an amplitude and a phase, and which contains information aboutthe spectrum of the radiation source 2900. The spectral analysiswavefront is subsequently imaged by imaging system 2920 to generate animage spectral analysis wavefront, which has an amplitude and a phase,and which contains information about the amplitude and phase of thespectral analysis wavefront. At least part of the radiation transmittedthrough element 2902 and imaged though imaging system 2920 is focusedvia a focusing lens 2904 onto a phase manipulator 2906, such as aspatial light modulator or a series of different transparent, spatiallynon-uniform objects, which is preferably located at the image plane ofradiation source 2900. It is appreciated that phase manipulator 2906 canbe configured such that a substantial part of the radiation focusedthereonto is reflected therefrom. Alternatively, the phase manipulator2906 can be configured such that a substantial part of the radiationfocused thereonto is transmitted therethrough.

A second lens 2908 is arranged so as to image element 2902 onto adetector 2910, such as a CCD detector. Preferably, the second lens 2908is arranged such that the detector 2910 lies in its focal plane. Theoutput of detector 2910, an example of which is a set of intensity mapsdesignated by reference numeral 2912, is preferably supplied to datastorage and processing circuitry 2914, which preferably carries out thethird sub-functionality described hereinabove with reference to FIG. 1,providing an output indicating at least one and possibly both of thephase and the amplitude of the image spectral analysis wavefront. Thisoutput is preferably further processed to obtain the phase and theamplitude of the spectral analysis wavefront and thus information aboutthe radiation source 2900, such as the spectrum of the radiationsupplied from radiation source 2900.

Preferably, the spectral analysis wavefront is obtained by reflectingthe radiation supplied from the image of the radiation source 2900 byelement 2902. Alternatively, the spectral analysis wavefront is obtainedby transmitting the radiation supplied from the image of the radiationsource 2900 through element 2902.

In accordance with an embodiment of the present invention, the beam ofradiation supplied from radiation source 2900 comprises a plurality ofdifferent wavelength components, thereby providing a plurality ofwavelength components in the spectral analysis wavefront andsubsequently in the transformed wavefront impinging on phase manipulator2906. In this case the phase manipulator may be an object, at least oneof whose thickness, refractive index and surface geometry variesspatially. This spatial variance of the phase manipulator generates adifferent spatial phase change for each of the wavelength components,thereby providing a plurality of differently phase changed transformedwavefronts to be subsequently detected by detector 2910.

In accordance with another embodiment of the present invention, thephase manipulator 2906 comprises a plurality of objects, eachcharacterized in that at least one of its thickness and refractive indexvaries spatially. The spatial variance of the thickness or of therefractive index of the plurality of objects may be selected in a waysuch that the phase changes applied by phase manipulator 2906 differ toa selected predetermined extent for at least some of the wavelengthcomponents supplied by radiation source 2900. The objects arespecifically selected such that the phase change applied to an expectedwavelength of the radiation source differs substantially from the phasechange applied to an actual wavelength of the radiation source.Alternatively, the spatial variance of the thickness or refractive indexof the plurality of objects may be selected in a way such that the phasechanges applied by phase manipulator 2906 are identical for at leastsome of the plurality of different wavelength components supplied byradiation source 2900.

In accordance with yet another embodiment of the present invention, theknown element 2902 comprises a plurality of objects, each characterizedin that at least one of its thickness and refractive index variesspatially. The spatial variance of the thickness or of the refractiveindex of the plurality of objects may be selected in a way such that thewavelength components of the input wavefront, generated by passing thewavelength components of the radiation supplied by radiation source 2900through the element 2902, differ to a selected predetermined extent forat least some of the wavelength components supplied by radiation source2900. The objects are specifically selected such that the wavelengthcomponent of the input wavefront generated by an expected wavelength ofthe radiation source differs substantially from the wavelength componentof the input wavefront generated by an actual wavelength of theradiation source. Alternatively, the spatial variance of the thicknessor refractive index of the plurality of objects may be selected in a waysuch that the wavelength components of the input wavefront, generated bypassing the wavelength components of the radiation supplied by radiationsource 2900 through the element 2902, are identical for at least some ofthe wavelength components supplied by radiation source 2900.

Reference is now made to FIG. 30, which is a general block diagram ofthe components of a preferred embodiment of the wavefront analysismodule performing the image wavefront analysis functionality of FIG. 25.As seen in FIG. 30, the illumination module consists of two differentlight sources 3002 with two different wavelengths. The illumination fromthe two light sources 3002 is combined by a beam combiner 3004 or otherconventional device and is collimated by a collimator 3006. Thecollimated beam is coupled by a beam splitter 3008 into the microscope3010 through the image plane 3012 and propagates through the microscopetube and illuminates the object 3014. The reflected light from theobject forms an image of the object 3014 in the microscope's image plane3012. This image's wavefront serves as an object for the wavefrontanalysis module 3016 and it is analyzed by the wavefront analysis module3016.

Preferably, the wavefront analysis module 3016 will include an opticalmanipulator 3018, imaging optics 3020 and a CCD camera 3022, andadditional components may be added for calibration of the opticalmanipulator location. Alternatively, additional optical elements may beincluded in the wavefront analysis module in order to adapt the firstoptical system's image plane and light source's image plane to thewavefront analysis module optical planes such as object's plane and thephase manipulator's plane. A field stop may be included in theintermediate image plane or in another plane within the optical head3030. The wavefront analysis module can include electronic modules suchas power supplies, light-source drivers and drivers for the opticalelement, as well as software modules such as control software, userinterface software, dedicated 3D measurement software and data analysis.

Reference is now made to FIG. 31, which is a simplified illustration ofan existing microscope 3102, working in reflection or transmission mode,including a wavefront analysis module 3104, in accordance with stillanother preferred embodiment of the present invention. The wavefrontanalysis module 3104 preferably interfaces with the microscope 3102similarly to a conventional CCD. The existing microscope 3102 performsan optical imaging of the object, and the wavefront analysis module 3104provides a quantitative wavefront analysis of the optical image obtainedby the microscope 3102, where in general the wavefront analysis module3104 is independent of the imaging module of the microscope 3102, bothin hardware and in performance.

In this embodiment, the intermediate image, obtained by the microscope3102 at the image plane, serves as an “object” for the wavefrontanalysis module 3104 and the wavefront of the image is analyzed. Thewavefront analysis module 3104 can be identical in size, mechanicalinterfaces, optical interfaces, functionality and form to a CCD camera,while additionally generating the wavefront analysis.

Preferably, the wavefront analysis module 3104 is mounted at the samelocation using the same mounting means as a conventional CCD camera,where the ‘object plane’ of the module is the image plane of theoriginal CCD. In this embodiment, the same camera is used for acquiringthe two dimensional conventional image and the intensity images for thewavefront analysis calculations. Alternatively, two cameras may be used,one for the wavefront analysis module and the second for theconventional two dimensional microscopy.

The light source utilized in this embodiment may be the microscope'slight source or an additional light source. The illumination may becoupled to the microscope through the conventional coupling port orthrough any other suitable port such as illuminating the object throughthe image plane.

Additionally, the wavefront analysis module can be attached to anysuitable imaging optical system such as a telescope.

Additionally, the wavefront analysis module, which analyzes the image'swavefront, may be implemented in any of the following modes, eitheralone or in combination. The wavefront analysis module may be added to acommercial microscope, where the optical imaging of the microscope,tube-lens and various objectives, is used for the two dimensionalimaging and the wavefront analysis module analyses the image'swavefront. Preferably, the wavefront analysis module is mounted in theconventional CCD location. Additionally or alternatively, the wavefrontanalysis module is coupled directly to a commercial objective, togenerate a complete wavefront analysis sensor. Alternatively oradditionally, the wavefront analysis module is coupled to a set ofvarious commercial objectives, such as with different magnifications, togenerate a complete wavefront analysis sensor with variousmagnifications and lateral resolutions. Additionally or alternatively,various wavefront analysis sensors, all having the same basic wavefrontanalysis module, are combined with various two dimensional imagingobjectives.

Preferably, lenses or other suitable optical elements may be added tothe optical system in order to adapt the wavefront analysis module toany microscope or any other optical system. These lenses or otheroptical elements may be added to cancel spherical wavefronts ofspherical objects, or to cancel wavefront deviations from a knownwavefront, such as a plane wave, as in a Tewman-Green interferometer.Additionally or alternatively, additional imaging lenses or otheroptical elements may be added, such as simple off-the-shelf lenses,prisms or other optical elements, or custom made optical elements, whichmay have a variety of focal lengths and numerical apertures.

The wavefront analysis module can have various magnifications, where theoverall system magnification is the product of the magnification of theimaging microscope and the magnification of the wavefront analysismodule. In one embodiment of the present invention, the wavefrontanalysis module has a one times magnification, and the overallmagnification of the system is determined by the magnification of themicroscope imaging system.

In accordance with another preferred embodiment of the presentinvention, the wavefront analysis module will include an opticalmanipulator to manipulate the optical transform of the wavefrontobtained by the microscope imaging system. The manipulations, of thewavefront's optical transform provided by the microscope imaging system,may be implemented in any of the following modes, either alone or incombination, using multiple sensors and multiple passive wavefrontmanipulators in multiple optical branches, using one sensor and oneactive wavefront manipulator, such as an active spatial light modulator,in one optical branch or using multiple sensors and multiple passive andactive wavefront manipulators in multiple optical branches.

Preferably, the optical manipulator within the wavefront analysis moduleis located in any desired plane where optical transforms of the image'scomplex amplitude are obtained. Alternatively, the optical manipulatoris located in the light source's image plane where the Fourier Transformof the image's complex amplitude is obtained.

Preferably, lenses or other suitable optical elements may be added tothe optical system in order to adapt the optical manipulator to variousobjectives that do not have the same exit-pupil location.

In the present embodiment, the optical manipulator can perform at leastone and possibly a combination of phase manipulation, intensitymanipulation and polarization manipulation. When phase manipulation isrequired, the optical manipulator may be an active phase manipulator,such as a phase light modulator, or a passive phase manipulator, such asphase retarder. When intensity manipulation is required, the opticalmanipulator may be an active intensity manipulator, such as a maskedphase manipulator.

Preferably, the image wavefront analysis functionality also includes anillumination radiation source, such as a light source, for generatingthe wavefront to be analyzed. Alternatively, the illumination is coupledto the imaging functionality microscope through an existing illuminationcoupling port of the imaging system, such as a microscope's conventionalcoupling port. Alternatively, the illumination is coupled throughanother suitable port, such as illuminating an object to be inspectedthrough the image plane. Additionally or alternatively, the imagingfunctionality includes an illumination radiation source, such as a lightsource, for generating the wavefront to be analyzed. In this embodiment,the image wavefront analysis functionality can utilize this illuminationto generate the wavefront to be analyzed.

Preferably, the illumination radiation source of the wavefront analysissystem is a monochromatic light source. The light source can be of anytemporal coherence—high, partial or none.

Preferably, the illumination radiation source of the wavefront analysissystem is a light source including one major wavelength. Alternatively,various major wavelengths are presented.

Additionally or alternatively, the illumination radiation source of thewavefront analysis system is generated by various levels ofspatially-coherent illumination having various shapes. These may includea highly spatial coherence light source, such as a point light source oran illumination generated by parallel illumination, a lower spatialcoherence light source comprised of several point sources, or a very lowspatial coherent light source comprised of an elongate shape.Preferably, the spatial manipulation of the optical manipulator issubstantially identical in shape to the spatial shape of theillumination.

In accordance with one embodiment of the present invention, an existingmicroscope, working in reflection or transmission mode, generates anoptical image of an illuminated object.

Preferably, the illumination light source that illuminates the object isthe original microscope's light source. Alternatively, an additionallight source is provided for the illumination of the wavefront analysismodule. This illumination can be Koehler illumination, Criticalillumination or any other suitable conventional illumination method.Alternatively, an illumination module may be provided as part of thewavefront analysis module or as an independent illumination module.

Preferably, the object's illumination is implemented using anywavelength in the electromagnetic spectrum that can be detected by asensor.

In a further embodiment of the present invention, a camera, such as aCCD camera, is used for obtaining intensity maps of the image wavefrontanalysis functionality. Preferably, the same camera is used to obtainboth the information on the wavefront to be analyzed, such as aconventional image, and the image wavefront, such as the intensity datafor the wavefront analysis calculations. Alternatively, a separatecamera, such as a CCD camera, is used for acquiring the results of theimage wavefront analysis functionality. In this embodiment, two camerasare be used, one to obtain the conventional image and a second to obtainthe intensity data for the wavefront analysis calculations. This twocamera embodiment may be implemented, for example, by a dual portmicroscope. These cameras may be provided as part of the wavefrontanalysis module or may be a camera that can be independently mounted onthe wavefront analysis module. Preferably, the camera consists of anychip-size of CCD, CMOS or other detecting technologies, and any numberof pixels in any pattern.

In one embodiment of the present invention, an optical element oroptical system may be inserted into the wavefront analysis module toview the optical manipulator plane.

Preferably, the imaged object can be tilted using a mechanical stage soas to minimize the tilt in the wavefront to be analyzed. Alternatively,the tilt minimization of the wavefront to be analyzed can be obtained bymoving the optical manipulator perpendicular to the optical axis.

In another preferred embodiment of the present invention, the wavefrontanalysis system is combined with confocal microscopy. In thisembodiment, the wavefront analysis system is implemented as a “4-F”imaging optical system, i.e. where tile distance between the object andthe image equals 4 times the focal distance of the imaging objectivelens. It is known that current imaging systems with high numericalapertures are sensitive to focal length variations. This results in animaging optical system that can be used as a confocal microscope, whichis very sensitive to focal length variations and is used for focalmeasurements, 3D measurements and slicing. In this embodiment, theconfocal microscope characteristics are incorporated into a wavefrontanalysis system, which is designed to have high numerical aperture sothat it is very sensitive to focal length variations. This combinedconfocal wavefront analysis system can measure the phase and amplitudeof a reflected or transmitted wavefront, and also provides theadvantages of a confocal microscope, with increased overall dynamicrange, i.e. the overall ‘depth’ of the inspected object that can bemeasured. A “deep” object can be measured by slices, scanning in the Zdimension, where in each wavefront analysis measurement a different‘slice’ is measured, and the entire object is measured similarly toconfocal microscopy measurements.

In still another preferred embodiment of the present invention, thewavefront analysis system and method is combined with the Micro-Moirélines method. In a wavefront analysis system using a single wavelengthlight source there is a 2π ambiguity in the results, i.e. the resultobtained is modulo 2π of the real phase, when obtaining, the phase ofthe wavefront being analyzed. As a result, the dynamic range ofmeasurements, in particular the surface difference between adjacentlocations of the inspected object, is limited by the wavelength of thelight source, since the height measured has also ambiguity. To increasethe dynamic range of the measurements, required in many applications,this embodiment of the present invention combines a wavefront analysissystem with the Moiré lines method for height measurements.

In the Moiré lines method, interference fringes or a grating areprojected onto the object. The object is then viewed from anotherdirection through another grating with the same spacing. The Moirépattern obtained by the two interfering lines series is used to obtainthe contour of the object. In the present embodiment, the object can beprojected, as in the Moiré lines method, by interference fringes orgrating lines and will be viewed by a sensor through another gratinghaving the same spacing as the grating lines. The contours obtained bythe Moiré pattern of the combined system are used to obtain the objectsurface topography with an increased measurement range, but with limitedresolution, while the different intensity images of the wavefrontanalysis system portion of the combined system are used to obtain theobject surface with a limited measurement range, but with increasedresolution. Thus, in the combined method and system the object's surfacetopography is obtained in an increased measurement range and increaseresolution.

Preferably, the projected lines are obtained by using two coherent lightsources with a fixed lateral distance between them. The two beamsinterfere and a fringe pattern is obtained on the object surface. A linephase filter is introduced in the Fourier plane as described inreference to FIG. 4 hereinabove, so that the two beams will experiencethe same phase delays. Alternatively, an image of a grating is projectedon the object. Since the light illuminating the object is spatiallymodulated before illuminating the object, this process does notinterfere with the phase-change analysis process of the wavefrontanalysis system.

Reference is now made to FIG. 32, which is a simplified partiallyschematic, partially pictorial illustration of a wavefront analysissystem operative to generate measurements in an extended Z range, inaccordance with yet another preferred embodiment of the presentinvention.

Current wavefront retrieval methods and algorithms includenon-interferometric methods, such as Shack-Hartman and the Gerchberg andSaxton algorithm, as well as interferometric methods, such as PhaseShift Interferometry (PSI), Point Diffraction Interferometry (PDI), orother conventional methods. The prior PCT and U.S. Provisional PatentApplications of the assignee cited hereinabove, provide other wavefrontanalysis methodologies and systems, as well as systems and methodologiesfor surface mapping, phase change analysis, spectral analysis, objectinspection, stored data retrieval, three-dimensional imaging and othersuitable applications utilizing wavefront analysis. Conventionalinterferometric methods are limited in the extent of the measurementrange due to the 2π ambiguity. The measurement range can be extendedsignificantly using mechanical scanning, but this method for rangeextension is limited in the measurement range and is time consuming. Itis known that Maxwell's equations have unique solutions, such that whena specific solution is known in an arbitrary plane, the solution in anyother plane is determined.

In accordance with a preferred embodiment of the present invention, theradiation complex amplitude can be analyzed or retrieved at an arbitraryplane and it can be propagated to any other desired plane by propagationformulas, known in the art. There are several propagation formulas for aradiation complex amplitude propagation from a certain plane p1 toanother plane p2, such as Fresnel Transform or Rayleigh-Sommerfeld andKirchhof diffraction integrals. The Rayleigh-Sommerfeld diffractionintegral is:

$\begin{matrix}{{{u\left( {x,y,z} \right)} = {\int{\int{\left\lbrack {{\overset{\sim}{U}\left( {f_{x},f_{y}} \right)}{\exp\left( {2\pi\;{\mathbb{i}f}_{z}} \right)}} \right\rbrack{\exp\left( {2\pi\;{{\mathbb{i}}\left( {{f_{x}x} + {f_{y}y}} \right)}} \right\rbrack}{\mathbb{d}f_{x}}{\mathbb{d}f_{y}}}}}}{where}} & (19.1) \\{{U\left( {f_{x},f_{y}} \right)} = {\int{\int{{u\left( {x,y,0} \right)}{\exp\left\lbrack {{- 2}\pi\;{{\mathbb{i}}\left( {{f_{x}x} + {f_{y}y}} \right)}} \right\rbrack}{\mathbb{d}x}{\mathbb{d}y}}}}} & (19.2) \\{f_{z} = \left\{ \begin{matrix}\left( {\frac{1}{\lambda^{2}} - f_{t}^{2}} \right)^{\frac{1}{2}} & {{{if}\mspace{14mu} f_{t}^{2}} = {{f_{x}^{2} + f_{y}^{2}} \leq \frac{1}{\lambda^{2}}}} \\\left( {f_{t}^{2} - \frac{1}{\lambda^{2}}} \right)^{\frac{1}{2}} & {{{if}\mspace{20mu} f_{t}^{2}} = {{f_{x}^{2} + f_{y}^{2}} \geq \frac{1}{\lambda^{2}}}}\end{matrix} \right.} & (19.3)\end{matrix}$Where

-   u(x,y,0) is the radiation complex amplitude at each point (x,y) in    the plane p1,-   u(x,y,z) is the radiation complex amplitude obtained at each point    (x,y) in the plane p2,-   z is the distance in the Z direction between planes p1 and p2, and-   λ is the wavelength.

The present invention enables an extended Z range of the wavefrontanalysis and retrieval to be obtained. For example, the complexamplitude of the wavefront can be retrieved by a conventional wavefrontretrieval method in a certain plane. By propagating the calculatedwavefront's complex amplitude by the propagation formulas to any otherdesired plane, an extended three dimensional and object's surfacemapping range is obtained without the need for additional scanning.

As seen in FIG. 32, a wavefront 3204 is generated by object 3200 in aplane 3202. In plane 3202 the complex amplitude of the radiation can bedescribed by the function A(x,y)e^(1φ(x,y)). The complex amplitude ofthe radiation in plane 3202 propagates further to plane 3206, formingpropagated wavefront 3208. As the wavefront's complex amplitudepropagates, the amplitude and the phase are changed and a differentcomplex amplitude, described by the function A′(x,y)e^(1φ′(x,y)), isobtained at plane 3206. If the wavefront is known in a certain plane, itcan be calculated in any other plane, by virtue of equations(19.1)-(19.3) above. The propagated wavefront 3208 is then focused, asby a lens 3210, onto a phase manipulator 3212, preferably located at thefocal plane of lens 3210. A second lens 3214 is arranged so as to imagethe wavefront onto a detector 3216, such as a camera or CCD detector.Preferably the second lens 3214 is arranged such that the detector 3216lies in its focal plane. The output of detector 3216 is preferablysupplied to data storage and processing circuitry 3218, which analysesthe propagated wavefront as described hereinabove with respect tovarious wavefront analysis methods. This propagated wavefront 3208 issubsequently back propagated by virtue of equations (19.1)-(19.3),described hereinabove, from plane 3206 to obtain wavefront 3204 at plane3202.

In accordance with the present embodiment, the data storage andprocessing circuitry 3218 is operative to propagate the wavefront'scomplex amplitude by the propagation formulas from one plane to anotherplane, such as from plane 3206 to plane 3202. By virtue of thispropagation, when obtaining the wavefront at any specific plane, allcharacterizations of the radiation, such as amplitude, phase andpolarization, in any second plane can be obtained by propagating thewavefront's complex amplitude by equations (19.1)-(19.3) to that secondplane. Therefore, there is no need to measure those characterizations inthat certain plane, and an extended three dimensional and surfacemapping range of the object without requiring additional scanning can beobtained.

Additionally, the measuring device needs not be focused onto the objectto be measured. The measured wavefront's complex amplitude, onceobtained at one plane, can be propagated by virtue of the propagationformulas from the measuring plane to any other desired plane, such asthe plane which is in focus, to obtain a focused image.

Additionally, when an object to be inspected has an extended height ordepth such that part of the surface of the object is within the depth offield and part of it is outside the depth of field, the measuring deviceneeds not be focused onto the part of the object which is outside thedepth of field. Additionally, there is no need to measure again the partof the object which is outside the depth of field. Rather, the measuredwavefront's complex amplitude at the plane within the depth of field canbe propagated from the measuring plane to any other desired plane toobtain a focused image of the part of the object which is outside thedepth of field.

Additionally, the present invention allows for obtaining the absolutedistance between the measuring plane and any other desired plane. Bypropagating the measured wavefront's complex amplitude from themeasuring plane to another plane to obtain a focused image, the distancethat the measured wavefront's complex amplitude was propagated is wellknown, i.e. the actual distance between these two planes.

Additionally, by propagating sequentially the measured wavefront'scomplex amplitude from the measuring plane to adjacent planes in smallsteps, a focused spatial part of the image at each plane can beobtained. This method enables even an optical system with narrow depthof focus to obtain a focused image with very large depth.

This embodiment of the present invention also provides more detailsabout the wavefront and a lateral super-resolution, by measuring thewavefront's complex amplitude at any other desired plane, and comparingit to the calculated wavefront's complex amplitude at that plane. Inaccordance with the present invention, by measuring the wavefront'scomplex amplitude at a defocus plane where the wavefront is expandedrelative to the focus plane, more detector's pixels are involved andconsequently more details about the wavefront can be determined. Whenthe wavefront measured at the defocus plane is propagated back to thefocus plane a better lateral resolution is obtained. In addition, when adiverging illumination is used, the divergent radiation complexamplitude can be measured in a certain plane. This measured radiationcomplex amplitude can be propagated back in the conversion direction toobtain the radiation complex amplitude with better lateral resolution.

It is well known that by using two wavelength measurements the 2πambiguity is resolved. By propagation of the two wavefronts, one foreach wavelength, an extended Z range with high resolution can becalculated. The basic measurements with the two wavelengths give a veryhigh resolution measurement where the 2π ambiguity is resolved. Thishigh resolution measurement is conserved during the propagation of theradiation complex amplitude. The radiation complex amplitude of eachwavelength can be propagated to any desired plane. In the desired planethe two obtained wavefronts can be recombined to resolve the 2πambiguity at that plane.

Additionally, the present invention can utilize the reconstructedwavefront's complex amplitude to obtain multiple views of interferencepatterns in different Z ranges by simulating multiple reference beamsimpinging on a virtual mirror. These multiple views are generated byinterfering a virtual reference beam impinging on the virtual mirrorwith the reconstructed complex amplitude. These multiple views allow fora three dimensional reconstruction of the original object.

Additionally, the present invention can utilize the reconstructedwavefront's complex amplitude to simulate other suitable applications,such as Shack-Hartman or confocal microscopy by propagating thereconstructed wavefront's complex amplitude to any required planethrough any virtual optical element. For instance, the reconstructedwavefront's complex amplitude can be propagated through a virtualmicro-lens array to obtain the intensity in the focus plane of thevirtual micro-lens array. This simulates the results of what is obtainedin a Shack-Hartman sensor. In another example, the reconstructedwavefront's complex amplitude can be propagated through a virtual lensthat focuses it to a pinhole. This produces a result similar to thatobtained by confocal microscopy.

Additionally, the present invention can utilize the reconstructedwavefront's complex amplitude to generate an extended focused Z rangewithout requiring additional scanning of the object, as opposed to theextended focused Z range generated by a conventional microscope, whichrequires scanning of the object.

Reference is now made to FIG. 33, which is a simplified, partiallyschematic, partially pictorial illustration of a wavefront analysissystem operative to provide, in addition to surface topography orwavefront analysis, the absolute location of an object with respect to areference mirror, in accordance with still another preferred embodimentof the present invention.

In some of the previous embodiments of a wavefront analysis systemdescribed hereinabove a relative wavefront is measured, i.e. where anarbitrary phase constant can be added to the entire complex wavefront.Thus, when an object surface is measured, a constant height can be addedto the entire surface, and the absolute location of the object inrespect to the measuring instrument is not known. In this embodiment,the phase constant added to the complex amplitude reconstructed isdetermined relative to a reference wavefront. Thus, for example, when anobject surface is measured, the distance from the object's surface tothe reference mirror within the measuring instrument is obtained.

As seen in FIG. 33, the optical apparatus is similar to that describedwith reference to FIG. 20, with a shutter 3305 and a reference mirror3307 added, and data storage and processing circuitry 3316 includesadditional functionalities. In the present apparatus, the incomingillumination from a radiation source 3300, after optionally beingexpanded by a beam expander 3302, is split by a beam splitter 3304. Partof the illumination is projected on an object 3306 to obtain thewavefront of the object. This part of illumination serves as theobject's beam. When shutter 3305 is in an open state, the other part ofthe illumination is projected onto reference mirror 3307 and serves as areference beam.

The object's beam is reflected from the object 3306 and focused via afocusing lens 3308 onto a phase manipulator 3310, such as a Phase LightModulator, which is preferably located at the image plane of radiationsource 3300. A second lens 3312 is arranged to image object 3306 onto adetector 3314, such as a CCD camera. Multiple images, preferably, threeor four images, are recorded by detector 3314 when the shutter 3305 isclosed. Each image corresponds to a different phase changes caused byphase modulator 3310. The output of detector 3314, such as a set ofintensity maps 3315, is preferably supplied to the data storage andprocessing circuitry 3316, which reconstructs the wavefront reflectedfrom the object as described hereinabove with respect to previousembodiments. In the current embodiment, an additional image 3318 isobtained on the detector 3314, in a state where no phase change isapplied by the phase manipulator 3310, and the shutter 3305 is open.This additional image is an intensity map of the interference pattern ofthe object's beam and the reference beam.

The data storage and processing circuitry 3316 employs the obtainedreconstructed wavefront reflected from the object, together with theadditional image 3318 and the known nature of the mirror 3307 to obtainthe absolute location of the surface of the object with respect toreference mirror 3307. This absolute distance is obtained by calculatingthe optimal phase constant that when added to the complex amplitude wheninterfering with the reference beam generates an intensity pattern asclose as possible to interference image 3318.

Obtaining the absolute location of each object with respect to thereference mirror, enables measuring the absolute distance between twodifferent objects that are far apart from each other by comparing theabsolute distance between each one of these objects to the referencemirror.

The additional measurement described hereinabove enables obtainingadditional data for the reconstructed wavefront that can be applied tocorrect the reconstructed wavefront.

The average absolute distance between the object to the reference mirroris calculated by averaging it over all the object's points. The actualdistance from each object's point to the reference mirror is the averageabsolute distance between the object to the reference mirror minus theheight of the object's point. Any deviation of the distance of eachpoint of the object from this calculated distance can be considered asan error in the height measurement of this point, and can be corrected.

Preferably, the illumination source contains more than one wavelength toresolve the 2π ambiguity.

According to the present invention, where there are estimated knowndifferences of the wavefront being analyzed from a planar-likewavefront, these estimated known differences can be removed by anoptical element. In this embodiment, the measurements are done on aplanar-like wavefront to obtain the complex amplitude of thisplanar-like wavefront, and to measure the deviations, such as in phaseand amplitude, of this planar-like wavefront from an ideal uniform planewave. When the complex amplitude of the planar-like wavefront isreconstructed, the estimated known differences that were removed arereintroduced mathematically to obtain the actual wavefront.

In another embodiment, when the wavefront being analyzed isapproximately a spherical wavefront, a lens can be added to remove thespherical components of the wavefront being analyzed. After thereconstruction, the removed spherical components are mathematicallyadded to the reconstructed wavefront, to obtain the wavefront beinganalyzed.

In another embodiment, where the wavefront being analyzed is a tiltedwavefront with additional features, a prism can be added to remove thetilt component of the wavefront being analyzed. After the wavefrontreconstruction, the removed tilt component is mathematically added tothe reconstructed wavefront to obtain the wavefront being analyzed.

The wavefront analysis systems and methods described hereinabove can beused in a variety of applications, including wavefront analysis, surfacemapping, phase change analysis, spectral analysis, object inspection,intensity retrieval, phase retrieval, polarization retrieval, storeddata retrieval, multilayer measurements, three-dimensional imaging andother suitable applications utilizing wavefront analysis. Theseapplications specifically include optical systems for 3D measurement andsurface mapping of various objects, such as semiconductors, electroniccomponents and micro-mechanical elements, optical systems for themeasurement of transparent objects, such as optical components, qualityof optical components, measurement of index of refraction and biologicaltissue, and optical system for spectral analysis.

The systems and methods described hereinabove provide a variety ofadvantages over conventional methods, including the flexibility providedby an independent wavefront analysis module and an independent imagingtwo dimensional module, the ability to utilize various magnificationsusing the same wavefront analysis module and the potential to enhancethe performance of a two dimensional microscope or to convert it into athree dimensional measurement tool. Additionally, the combination ofconventional two dimensional imaging and wavefront analysis, such as byutilizing three dimensional surface mapping, is advantageous to the userdue to the ability to view in a conventional microscope the area whichis being measured. Furthermore, the present invention describes awavefront analysis system which is robust and insensitive to vibrations,unlike a conventional interferometer. Quantitative three dimensionalimaging with nano-meter accuracy in the height axis can be obtained, aswell as high throughput two and three dimensional measurements.Additionally, the present invention provides the ability to adapt awavefront analysis module to any other optical system. The combinationof various measurements, such as that obtained by conventional imaging,with the intensity data from the wavefront analysis, can be utilized toextract information, not readily obtainable by conventional methods froman object being analyzed. Additionally, as described hereinabove, theobtained wavefront parameters, such as amplitude and phase, can beaveraged to eliminate fringes and other noise factors to obtain a moreaccurate measurement, using different channels and/or differentwavelengths.

The present invention also provides elaborated, improved and enhancedmethodologies and systems for wavefront analysis. Additionally, thepresent invention provides methods and systems to perform wavefrontanalysis and three dimensional measurements, specifically those whichare based on analyzing the output of an intermediate plane, such as animage plane, of an optical system. These methods and systems can beapplied to existing wavefront analysis and measurement methods, such asmethods provided in PCT Application No. PCT/IL/01/00335, and in U.S.Provisional Patent Applications, Ser. Nos. 60/351,753 and 60/406,593, ofthe assignee, as well as other conventional wavefront analysis methods.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove as well as variations and modifications whichwould occur to persons skilled in the art upon reading thespecifications and which are not in the prior art.

1. A method of wavefront analysis comprising: utilizing a light sourceto illuminate an object and to obtain a wavefront having an amplitudeand a phase; obtaining a plurality of differently phase changedtransformed wavefronts corresponding to said wavefront being analyzed,including: applying a transform to said wavefront being analyzed therebyto obtain a transformed wavefront; and applying a plurality of differentphase changes to said transformed wavefront, thereby to obtain aplurality of differently phase changed transformed wavefronts; obtaininga plurality of intensity maps of said plurality of phase changedtransformed wavefronts by phase manipulation; and employing saidplurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, wherein saidplurality of different phase changes are applied to a region of saidtransformed wavefront, said region having a shape of said light source.2. A method according to claim 1 and wherein said light source comprisesan elongate light source.
 3. A method of wavefront analysis comprising:utilizing a light source to illuminate an object and to obtain awavefront having an amplitude and a phase; obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to saidwavefront being analyzed, including: applying a transform to saidwavefront being analyzed thereby to obtain a transformed wavefront; andapplying a plurality of different phase changes to said transformedwavefront, thereby to obtain a plurality of differently phase changedtransformed wavefronts; obtaining a plurality of intensity maps of saidplurality of phase changed transformed wavefronts by phase manipulation;and employing said plurality of intensity maps to obtain an outputindicating said amplitude and phase of said wavefront being analyzed,wherein said plurality of different phase changes are applied to regionsof said transformed wavefront, said regions having the form of agrating.
 4. A method of wavefront analysis comprising: obtaining aplurality of differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed which has an amplitude and aphase; obtaining a plurality of intensity maps of said plurality ofphase changed transformed wavefronts; and employing said plurality ofintensity maps to obtain an output indicating said amplitude and phaseof said wavefront being analyzed, and wherein obtaining a plurality ofdifferently phase changed transformed wavefronts comprises: applying atransform to said wavefront being analyzed thereby to obtain atransformed wavefront; and applying a plurality of different phasechanges to said transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein saidtransformed wavefront comprises a plurality of different polarizationcomponents; and said plurality of different phase changes are effectedby using a birefringent phase changer to apply different phase changesto said plurality of different polarization components of saidtransformed wavefront.
 5. A method of wavefront analysis comprising:obtaining two differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed which has an amplitude and aphase; obtaining two intensity maps of said two phase changedtransformed wavefronts; employing interference between said twointensity maps to generate a third intensity map; and employing said twointensity maps and said third intensity map to obtain an outputindicating said amplitude and phase of said wavefront being analyzed. 6.A method of wavefront analysis comprising: obtaining a plurality ofdifferently phase changed transformed wavefronts corresponding to awavefront being analyzed which has an amplitude and a phase; obtaining aplurality of intensity maps of said plurality of phase changedtransformed wavefronts; and employing said plurality of intensity mapsto obtain an output indicating said amplitude and phase of saidwavefront being analyzed, and wherein obtaining a plurality ofdifferently phase changed transformed wavefronts comprises: applying atransform to said wavefront being analyzed thereby to obtain atransformed wavefront; and applying a plurality of different phasechanges to said transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts, and wherein: saidplurality of different phase changes includes spatial phase changes;said plurality of different spatial phase changes are effected byapplying a spatially uniform, time-varying spatial phase change to partof said transformed wavefront; said transform applied to said wavefrontbeing analyzed is a Fourier transform; said plurality of differentspatial phase changes comprises at least three different phase changes,said plurality of intensity maps comprises at least three intensitymaps; and said employing step comprises: expressing said wavefront beinganalyzed as a first complex function which has an amplitude and phaseidentical to said amplitude and phase of said wavefront being analyzed;expressing said plurality of intensity maps as a function of said firstcomplex function and of a spatial function governing said spatiallyuniform, time-varying spatial phase change; defining a second complexfunction, having an absolute value and a phase, as a convolution of saidfirst complex function and of a Fourier transform of said spatialfunction governing said spatially uniform, time-varying spatial phasechange; expressing each of said plurality of intensity maps as a thirdfunction of: said amplitude of said wavefront being analyzed; a squareof said absolute value of said second complex function; a differencebetween said phase of said wavefront being analyzed and said phase ofsaid second complex function; and a known phase delay produced by one ofsaid at least three different phase changes which each correspond to oneof said at least three intensity maps; solving said third function toobtain said amplitude of said wavefront being analyzed, said absolutevalue of said second complex function and said difference between saidphase of said wavefront being analyzed and said phase of said secondcomplex function; solving said second complex function to obtain saidphase of said second complex function; and obtaining said phase of saidwavefront being analyzed by adding said phase of said second complexfunction to said difference between said phase of said wavefront beinganalyzed and said phase of said second complex function, said square ofsaid absolute value of said second complex function is obtained byapproximating a square of said absolute value to a polynomial of a givendegree; and said employing step comprises computing a confidence levelmap characterizing confidence in each of a plurality of portions of saidphase of said wavefront being analyzed, by comparing said square of saidabsolute value of said second complex function to said polynomial of agiven degree, the confidence level map comprising a plurality ofconfidence levels respectively corresponding to a plurality of portionswithin said intensity maps.
 7. A method according to claim 6 whereinsaid step of applying a plurality of different phase changes isperformed at least twice using at least two pluralities of differentphase changes and wherein said step of employing is performed at leasttwice using said at least two pluralities of different phase changes,thereby to obtain at least two values for said phase of said wavefrontbeing analyzed, and wherein the method also comprises using the at leasttwo confidence level maps resulting from performing said confidencelevel map computation step at least twice, to combine said at least twovalues for said phase of said wavefront being analyzed into a singlevalue.
 8. A method according to claim 7 wherein said step of combiningcomprises selecting one value from among said at least two values forsaid phase of said wavefront being analyzed, wherein said selected valueis the value of the phase having the highest value of said confidencelevels.
 9. A method according to claim 7 wherein said step of combiningcomprises computing a weighted average of said at least two values forsaid phase of said wavefront being analyzed, using the confidence levelsincluded in said at least two confidence level maps as weights for theat least two values respectively.
 10. A method according to claim 6 andalso comprising computing the confidence in each of a plurality ofportions of said phase, using, for at least one portion, a phase valuewhich is different from that measured for the at least one portion and,if the confidence computed for an individual portion using the differentphase value exceeds the confidence computed using the measured phasevalue, replacing the measured phase value for the individual portionwith the different phase value.
 11. A method according to claim 6wherein the wavefront being analyzed comprises a plurality of wavefrontcomponents having different wavelengths, and said plurality ofdifferently phase changed transformed wavefronts are obtained byapplying a phase change to said plurality of different wavelengthcomponents of said wavefront being analyzed, and wherein said wavefrontbeing analyzed comprises a plurality of different wavelength components;and said plurality of differently phase changed transformed wavefrontsare obtained by applying a phase change to said plurality of differentwavelength components of said wavefront being analyzed.
 12. A methodaccording to claim 11 wherein said step of applying a plurality ofdifferent phase changes is performed for each of the plurality ofwavefront components, and wherein said step of employing is performedfor each of the plurality of wavefront components, thereby to obtain acorresponding plurality of values for said phase of said wavefront beinganalyzed, and wherein the method also comprises using the at leastconfidence level maps resulting from performing said confidence levelmap computation step a plurality of times, to combine said plurality ofvalues for said phase of said wavefront being analyzed into a singlevalue.
 13. A method of wavefront analysis comprising: obtaining aplurality of differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed which has an amplitude and aphase; obtaining a plurality of intensity maps of said plurality ofphase changed transformed wavefronts; and employing said plurality ofintensity maps to obtain an output indicating said amplitude and phaseof said wavefront being analyzed, and wherein said step of employingalso comprises normalizing each of the plurality of intensity maps toobtain a plurality of intensity maps having the same sum of intensityvalues.
 14. A method according to claim 13 and wherein said plurality ofdifferently phase changed transformed wavefronts are obtained so as tomaximize contrast between said plurality of intensity maps and tominimize effects of noise on said phase of said wavefront beinganalyzed.
 15. A method of phase change analysis comprising: obtaining aphase change analysis wavefront which has an amplitude and a phase;applying a transform to said phase change analysis wavefront thereby toobtain a transformed wavefront; applying at least one phase change tosaid transformed wavefront, thereby to obtain at least one phase changedtransformed wavefront; obtaining at least one intensity map of said atleast one phase changed transformed wavefront; and employing said atleast one intensity map to obtain an output indication of said at leastone phase change applied to said transformed phase change analysiswavefront.
 16. A method according to claim 15 and wherein said obtaininga phase change analysis wavefront comprises reflecting light off a knownobject and using the light reflected off the known object as said phasechange analysis wavefront.
 17. A method according to claim 15 andwherein said obtaining a phase change analysis wavefront comprisestransmitting light through a known object and using the transmittedlight exiting the known object as said phase change analysis wavefront.18. A method according to claim 15 and wherein said applying at leastone phase change to said transformed wavefront comprises applying aphase delay value to an area within said transformed wavefront andwherein said step of employing said at least one intensity map comprisesobtaining an output indication delimiting said area.
 19. A methodaccording to claim 18 wherein said obtaining a phase change analysiswavefront comprises reflecting light off a known object and using thelight reflected off the known object as said phase change analysiswavefront.
 20. A method according to claim 18 wherein said obtaining aphase change analysis wavefront comprises transmitting light through aknown object and using the transmitted light exiting the known object assaid phase change analysis wavefront.
 21. A method according to claim 15wherein said step of employing said at least one intensity map comprisesderiving at least one contrast map from the at least one intensity mapand employing said at least one contrast map to obtain an outputindication of said at least one phase change applied to said transformedphase change analysis wavefront.
 22. A method of wavefront analysiscomprising: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas an amplitude and a phase; obtaining a plurality of intensity maps ofsaid plurality of phase changed transformed wavefronts; and employingsaid plurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, the method alsocomprising: performing said obtaining steps and said employing stepwherein said wavefront being analyzed comprises a wavefront originatingfrom a known object having known amplitude and phase values; computingamplitude and phase calibration values by comparing the output of theemploying step performed on said known object to said known amplitudeand phase values; and when performing said obtaining and employing stepson an unknown object, using said amplitude and phase calibration valuesto correct the output for said unknown object generated in saidemploying step.
 23. A method according to claim 22 wherein saidwavefront originating from the known object comprises a wavefrontreflected from the known object.
 24. A method according to claim 22wherein said wavefront originating from the known object comprises awavefront transmitted through the known object.
 25. A method accordingto claim 22 wherein said known object comprises a flat mirror.
 26. Amethod according to claim 22 wherein said known object comprises awindow.
 27. A method of wavefront analysis comprising: obtaining aplurality of differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed which has an amplitude and aphase; obtaining a plurality of intensity maps of said plurality ofphase changed transformed wavefronts; and employing said plurality ofintensity maps to obtain an output indicating said amplitude and phaseof said wavefront being analyzed, and also comprising using an iris toblock off a portion of a wavefront, thereby to generate said wavefrontbeing analyzed, and wherein the plurality of intensity maps are obtainedusing a camera having an imaging area which is larger than the image ofsaid iris on the imaging area.
 28. A method of wavefront analysiscomprising: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas an amplitude and a phase; obtaining a plurality of intensity maps ofsaid plurality of phase changed transformed wavefronts; and employingsaid plurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, and whereinobtaining a plurality of differently phase changed transformedwavefronts comprises: applying a transform to said wavefront beinganalyzed thereby to obtain a transformed wavefront; and applying aplurality of different phase changes to said transformed wavefront,thereby to obtain a plurality of differently phase changed transformedwavefronts, and wherein said plurality of different phase changesincludes spatial phase changes, and wherein said plurality of differentspatial phase changes are effected by applying a spatially uniform,time-varying spatial phase change to part of said transformed wavefront,and wherein: said transform applied to said wavefront being analyzed isa Fourier transform; said step of employing includes: expressing saidwavefront being analyzed as a first complex function which has anamplitude and phase identical to said amplitude and phase of saidwavefront being analyzed; expressing said plurality of intensity maps asa function of said first complex function and of a spatial functiongoverning said spatially uniform, time-varying spatial phase change;defining a second complex function, having an absolute value and aphase, as a convolution of said first complex function and of a Fouriertransform of said spatial function governing said spatially uniform,time-varying spatial phase change; expressing each of said plurality ofintensity maps as a third function of: said amplitude of said wavefrontbeing analyzed; said absolute value of said second complex function; adifference between said phase of said wavefront being analyzed and saidphase of said second complex function; and a known phase delay producedby one of said different phase changes which each correspond to one ofsaid intensity maps; solving said third function to obtain saidamplitude of said wavefront being analyzed, said absolute value of saidsecond complex function and said difference between said phase of saidwavefront being analyzed and said phase of said second complex function;solving said second complex function to obtain said phase of said secondcomplex function; and obtaining said phase of said wavefront beinganalyzed by adding said phase of said second complex function to saiddifference between said phase of said wavefront being analyzed and saidphase of said second complex function, wherein said step of obtaining anoutput indicating said amplitude and phase of said wavefront beinganalyzed comprises employing said plurality of intensity maps and saidsquare of the absolute value of the second complex function to obtainsaid output.
 29. A method for analyzing a wavefront having an amplitudeand a phase, the method comprising: using an iris to block off a portionof a wavefront, thereby to generate a wavefront being analyzed;Fourier-transforming said wavefront being analyzed and effecting aspatial phase change on a portion of the transformed wavefront, therebyto generate at least one partially phase changed transformed wavefront,including a known phase changed wavefront portion and a phase unchangedwavefront portion; obtaining at least one intensity map of said at leastone partially phase changed transformed wavefront, the map representinginterference between the phase changed portion and the phase unchangedportion, wherein said map is obtained using a camera having an imagingarea which is larger than the image of said iris on the imaging area,thereby to define inside and outside map portions representing intensityof light impinging on the imaging area portion inside and outside theiris image respectively; and employing said at least one intensity mapto obtain an output indicating said amplitude and phase of saidwavefront being analyzed, including: expressing said wavefront beinganalyzed as a first complex function which has an amplitude and phaseidentical to said amplitude and phase of said wavefront being analyzed;expressing said intensity map as a function of said first complexfunction and of a spatial function; and defining a second complexfunction, having an absolute value and a phase, as a convolution of saidfirst complex function and of a Fourier transform of said spatialfunction; wherein said absolute value of said second complex function isobtained by approximating said absolute value to a polynomial of a givendegree, and wherein the square of the absolute value of the secondcomplex function is derived from the portion of the imaging area whichis external to the image of said iris on the imaging area, assuming thatthe phase of the second complex function is constant over the imagingarea; and computing the amplitude and phase of the wavefront beinganalyzed by assuming said inside map portion represents interferencebetween said wavefront being analyzed and a wavefront having saidabsolute value of said second complex function as an amplitude andhaving a phase which is constant over the imaging area.
 30. A methodaccording to claim 27 and wherein: said obtaining a plurality ofdifferently phase changed transformed wavefronts comprises: applying atransform to said wavefront being analyzed thereby to obtain atransformed wavefront; and applying a plurality of different phasechanges to said transformed wavefront, thereby to obtain a plurality ofdifferently phase changed transformed wavefronts; said plurality ofdifferent phase changes includes spatial phase changes; said pluralityof different spatial phase changes are effected by applying a spatiallyuniform, time-varying spatial phase change to part of said transformedwavefront; said transform applied to said wavefront being analyzed is aFourier transform, said plurality of different spatial phase changescomprises at least three different phase changes; said plurality ofintensity maps comprises at least three intensity maps; and saidemploying includes: expressing said wavefront being analyzed as a firstcomplex function which has an amplitude and phase identical to saidamplitude and phase of said wavefront being analyzed; expressing saidplurality of intensity maps as a function of said first complex functionand of a spatial function governing said spatially uniform, time-varying spatial phase change; defining a second complex function, havingan absolute value and a phase, as a convolution of said first complexfunction and of a Fourier transform of said spatial function governingsaid spatially uniform, time-varying spatial phase change; expressingeach of said plurality of intensity maps as a third function of: saidamplitude of said wavefront being analyzed; said absolute value of saidsecond complex function; a difference between said phase of saidwavefront being analyzed and said phase of said second complex function;and a known phase delay produced by one of said at least three differentphase changes which each correspond to one of said at least threeintensity maps; solving said third function to obtain said amplitude ofsaid wavefront being analyzed, said absolute value of said secondcomplex function and said difference between said phase of saidwavefront being analyzed and said phase of said second complex function;solving said second complex function to obtain said phase of said secondcomplex function; and obtaining said phase of said wavefront beinganalyzed by adding said phase of said second complex function to saiddifference between said phase of said wavefront being analyzed and saidphase of said second complex function, and wherein the square of theabsolute value of the second complex function is derived from theportion of the imaging area which is external to the image of said irison the imaging area.
 31. A method of wavefront analysis comprising:obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase; obtaining a plurality of intensity maps of saidplurality of phase changed transformed wavefronts; and employing saidplurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, and whereinobtaining a plurality of differently phase changed transformedwavefronts comprises: applying a transform to said wavefront beinganalyzed thereby to obtain a transformed wavefront; and applying aplurality of different phase changes to said transformed wavefront,thereby to obtain a plurality of differently phase changed transformedwavefronts, and wherein said plurality of different phase changesincludes spatial phase changes, and wherein said plurality of differentspatial phase changes are effected by applying a spatial phase change topart of said transformed wavefront, wherein said step of applying aplurality of different phase changes comprises duplicating thetransformed wavefront into several wavefronts and wherein said step ofapplying a plurality of different phase changes comprises applying adifferent spatial phase change to each of said several wavefronts.
 32. Amethod according to claim 31 wherein said step of duplicating comprisessplitting the beam forming the transformed wavefront.
 33. A method ofproviding simultaneous surface and layer thickness measurements of amultilayer object comprising: illuminating the multilayer object withbroadband illumination; analyzing illumination emerging from saidmultilayer object to provide a spectral analysis output; and utilizingsaid spectral analysis output to provide simultaneously both surface andlayer thickness information regarding said multilayer object.
 34. Amethod according to claim 33 and wherein said method comprises:obtaining a reflected wavefront having an amplitude and a phase, byreflecting radiation from a surface; and analyzing said reflectedwavefront by: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to said reflected wavefront;obtaining a plurality of intensity maps of said plurality of phasechanged transformed wave fronts; and employing said plurality ofintensity maps to obtain an output indicating said amplitude and phaseof said reflected wavefront.
 35. A method according to claim 34 andwherein said radiation reflected from said surface has at least twonarrow bands, each centered about a different wavelength, providing atleast two wavelength components in said surface mapping wavefront and atleast two indications of said phase of said surface mapping wavefront,thereby enabling an enhanced mapping of said surface to be obtained byavoiding an ambiguity in the mapping which exceeds the larger of saiddifferent wavelengths about which said two narrow bands are centered.36. A method according to claim 34 and wherein: said wavefront beinganalyzed comprises a plurality of different wavelength components; andsaid plurality of differently phase changed transformed wavefronts areobtained by applying a phase change to said plurality of differentwavelength components of said wavefront being analyzed.
 37. A method ofwavefront analysis according to claim 34 and wherein: said plurality ofintensity maps comprises at least four intensity maps; and employingsaid plurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed includes employinga plurality of combinations, each of at least three of said plurality ofintensity maps, to provide a plurality of indications of said amplitudeand phase of said wavefront being analyzed.
 38. A method according toclaim 34 and wherein: said wavefront being analyzed comprises at leasttwo wavelength components; said obtaining a plurality of intensity mapsalso includes dividing said phase changed transformed wavefrontsaccording to said at least two wavelength components in order to obtainat least two wavelength components of said phase changed transformedwavefronts and in order to obtain at least two sets of intensity maps,each set corresponding to a different one of said at least twowavelength components of said phase changed transformed wavefronts; andemploying said plurality of intensity maps to obtain an outputindicating said amplitude and phase of said wavefront being analyzedincludes obtaining an output indicative of the phase of said wavefrontbeing analyzed from each of said at least two sets of intensity maps andcombining said outputs to provide an enhanced indication of phase ofsaid wavefront being analyzed, in which enhanced indication, there is noambiguity.
 39. A method according to claim 33 wherein said broadbandillumination includes multi-wavelength illumination includingillumination having a number of known wavelengths, said number at leastequal to the number of layers in said multilayer object.
 40. A methodaccording to claim 39 wherein said analyzing comprises generating anemerging illumination intensity map for each of a number of knownwavelengths, said number at least equal to the number of layers in saidmultilayer object.
 41. A method according to claim 39 wherein saidemerging illumination comprises at least one of reflected illuminationand transmitted illumination.
 42. A method of analyzing a wavefront,comprising a plurality of different wavelength components, after thewavefront exits an object, the method comprising: obtaining a pluralityof differently phase changed transformed wavefronts corresponding to awavefront being analyzed which has an amplitude and a phase, including:applying a transform to each of the plurality of different wavelengthcomponents, thereby to generate a plurality of transformed wavefrontcomponents; and applying a plurality of scalable phase changes to theplurality of transformed wavefront components respectively; obtaining aplurality of intensity maps of said plurality of phase changedtransformed wavefronts; and employing said plurality of intensity mapsto obtain an output indicating said amplitude and phase of saidwavefront being analyzed.
 43. A method according to claim 42 whereinsaid plurality of scalable phase changes are each in a different plane.44. A method according to claim 42 wherein said plurality of differentwavelength components are generated by light sources disposed at variousdistances from the object.
 45. A method of wavefront analysiscomprising: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas an amplitude and a phase; obtaining a plurality of intensity maps ofsaid plurality of phase changed transformed wavefronts; and employingsaid plurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, and whereinobtaining a plurality of differently phase changed transformedwavefronts comprises: applying a transform to said wavefront beinganalyzed thereby to obtain a transformed wavefront; and applying aplurality of different phase changes to said transformed wavefront,thereby to obtain a plurality of differently phase changed transformedwavefronts, wherein said applying a plurality of different phase changescomprises providing an optical system having a selectable plurality ofoptical configurations creating a corresponding plurality of phasechanges respectively.
 46. A method according to claim 45 wherein saidoptical system comprises a spatial light modulator (SLM) including acentral inactive area and a peripheral active area.
 47. A methodaccording to claim 45 wherein said optical system comprises a phaseplate having a plurality of portions each corresponding to an individualphase change and a phase plate portion selector operative to position aselected one of the phase plate portions along a light path.
 48. Themethod according to claim 45 wherein said optical system comprises twomirrors at an adjustable distance from one another whose relativeconfiguration is such that a first portion of the light impinging at thetwo mirror configuration arrives at the first mirror and a secondportion of the light impinging at the two mirror configuration arrivesat the second mirror, and wherein said distance between said two mirrorsis adjusted to effect said phase change.
 49. The method according toclaim 48 wherein said two mirrors comprise a first mirror preceding asecond mirror along the light path, said first mirror having an aperturedefined therewith, thereby allowing said second portion of the light toreach said second mirror via the aperture.
 50. The method according toclaim 48 wherein said two mirrors comprise a first mirror preceding asecond mirror along the light path wherein at least one dimension of thefirst mirror's surface area is less than at least one correspondingdimension of the cross-section of the wavefront and less than thecorresponding dimension of the second mirror's surface area, therebyallowing said second portion of the light to reach the second mirror.51. The method according to claim 48 and also comprising at least onepiezo-electric actuator operative to allow a user to control thedistance between the two mirrors.
 52. An apparatus for wavefrontanalysis comprising: a light source, to illuminate an object and toobtain a wavefront having an amplitude and a phase; a wavefronttransformer, obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzedhaving a phase and an amplitude, including: a transformed wavefrontgenerator, applying a transform to said wavefront being analyzed therebyto obtain a transformed wavefront; and a phase changer, applying aplurality of different phase changes to said transformed wavefront,thereby to obtain a plurality of differently phase changed transformedwavefronts; an intensity map provider, obtaining a plurality ofintensity maps of said plurality of phase changed transformed wavefrontsby phase manipulation; and an intensity map utilizer, employing saidplurality of intensity maps to obtain an output indicating saidamplitude and phase of said wavefront being analyzed, wherein saidplurality of different phase changes are applied to a region of saidtransformed wavefront, corresponding to a shape of said light source.53. An apparatus for wavefront analysis comprising: a wavefronttransformer, obtaining two differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase; an intensity map provider, obtaining twointensity maps of said two phase changed transformed wavefronts; and anintensity map utilizer, employing said two intensity maps to obtain anoutput indicating said amplitude and phase of said wavefront beinganalyzed; and wherein: said intensity map provider is also operative foremploying interference between said two intensity maps to generate athird intensity map; and said obtaining two differently phase changedtransformed wavefronts comprises: applying a transform to said wavefrontbeing analyzed thereby to obtain a transformed wavefront; and applying aplurality of different phase changes to said transformed wavefront,thereby to obtain a plurality of differently phase changed transformedwavefronts.
 54. A method of optical property analysis of an object byanalyzing a wavefront exiting the object, the method comprising:providing an imaging system having a defined depth of focus; repeatingthe following steps focusing on each of several depths within theobject: obtaining a plurality of differently phase changed transformedwavefronts corresponding to a wavefront being analyzed which has anamplitude and a phase and which is exiting an object; obtaining aplurality of intensity maps of said plurality of phase changedtransformed wavefronts; and employing said plurality of intensity mapsto obtain an output indicating said amplitude and phase of saidwavefront being analyzed; and combining the several outputs generated byrepeating said obtaining and employing steps in order to obtain aslice-by-slice optical transmission profile of the object.
 55. A methodaccording to claim 54 wherein said optical transmission profilecomprises an optical path length for each of the several depths withinthe object.
 56. A method of wavefront analysis operative to analyze awavefront exiting from an object, the method comprising: focusing animaging system on the object without changing the distance from theobject to the imaging system and obtaining a plurality of differentlyphase changed transformed wavefronts corresponding to a wavefront beinganalyzed which has an amplitude and a phase; obtaining a plurality ofintensity maps of said plurality of phase changed transformedwavefronts; and employing said plurality of intensity maps to obtain anoutput indicating said amplitude and phase of said wavefront beinganalyzed.
 57. A method of wavefront analysis comprising: obtaining aplurality of differently phase changed transformed wavefrontscorresponding to a wavefront being analyzed; obtaining a plurality ofintensity maps of said plurality of phase changed transformedwavefronts; and employing said plurality of intensity maps to obtain amodulo 2 output indicating said amplitude and phase of said wavefrontbeing analyzed, wherein said step of employing comprises computing atleast one characteristic of the object's surface geometry by analyzing aMoiré pattern generated by projecting stripes on the object and viewingthe object through a grating; and resolving the 2π ambiguity of themodulo 2π output using at least one characteristic of the object'ssurface geometry.
 58. A method according to claim 57 wherein saidstripes are generally linear.
 59. A method according to claim 57 whereinsaid step of projecting stripes comprises illuminating the object via agrating.
 60. A method according to claim 57 wherein said step ofprojecting stripes comprises using a plurality of coherent illuminationsources to illuminate the object, thereby to generate an interferencepattern on the object.
 61. A method for wavefront analysis utilizing apropagated wavefront, the method comprising: utilizing a propagatedwavefront, which corresponds to a wavefront being analyzed, having anamplitude and a phase, for obtaining a plurality of differently phasechanged transformed propagated wavefronts; obtaining a plurality ofintensity maps of said plurality of phase changed transformed propagatedwavefronts; and employing said plurality of intensity maps to obtain anoutput indicating said amplitude and phase of said wavefront beinganalyzed.
 62. A method for wavefront analysis according to claim 61 andwherein said employing comprises: employing said plurality of intensitymaps to obtain an output corresponding to said propagated wavefront; andemploying said output corresponding to said propagated wavefront toobtain an output indicating said amplitude and phase of said wavefrontbeing analyzed.
 63. A method according to claim 61 and also comprising:utilizing said output indicating said amplitude and phase of saidwavefront being analyzed in order to obtain a second output indicatingamplitude and phase of a propagated wavefront obtained by propagatingsaid wavefront being analyzed to any given plane.
 64. A method accordingto claim 63 wherein said propagating said wavefront being analyzed toany given plane also includes propagating through optical elements. 65.A method for wavefront analysis comprising: in a first mode ofoperation: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to an wavefront being analyzedwhich has an amplitude and a phase; obtaining a plurality of intensitymaps of said plurality of phase changed transformed wavefronts; andemploying said plurality of intensity maps to obtain an outputindicating said amplitude and phase of said wavefront being analyzed;and in a second mode of operation: carrying out an interferometricmeasurement on said wavefront being analyzed employing a reference inorder to provide an output indicating the location of a source of saidwavefront being analyzed.
 66. A method of wavefront analysis accordingto claim 65 and wherein said source of said wavefront being analyzedcomprises an object.
 67. A method of wavefront analysis according toclaim 65 and wherein said reference comprises a mirror.
 68. A method ofwavefront analysis comprising: obtaining a wavefront being analyzedwhich has an amplitude and a phase; obtaining a modified wavefront whichhas an amplitude and a phase in which estimated known differences of thewavefront being analyzed from a planar-like wavefront are removed by anoptical element; obtaining a plurality of differently phase changedtransformed modified wavefronts corresponding to said modifiedwavefront; obtaining a plurality of intensity maps of said plurality ofphase changed transformed modified wavefronts; employing said pluralityof intensity maps to obtain an output indicating said amplitude andphase of said modified wavefront; and obtaining an output indicatingsaid amplitude and phase of said wavefront being analyzed, byreintroducing said estimated known differences from said planar-likewavefront to said output indicating said amplitude and phase of saidmodified wavefront.
 69. A method according to claim 68 and wherein: saidwavefront being analyzed is approximately a spherical wavefront; andsaid optical element is a lens operative to remove the sphericalcomponents of said wavefront being analyzed.
 70. A method according toclaim 68 and wherein: said wavefront being analyzed is a tiltedwavefront with additional features, and said optical element is a prismoperative to remove the tilt component of said wavefront being analyzed.71. A wavefront analysis system comprising: a wavefront generator,operative to obtain a wavefront being analyzed which has an amplitudeand a phase; an optical element, operative to modify said wavefront toobtain a modified wavefront which has an amplitude and a phase in whichestimated known differences of the wavefront being analyzed from aplanar-like wavefront are removed by said optical element; a phasechanger, operative to provide a plurality of differently phase changedtransformed modified wavefronts corresponding to said modifiedwavefront; an intensity map generator, operative to generate a pluralityof intensity maps of said plurality of phase changed transformedmodified wavefronts; an intensity map utilizer, employing said pluralityof intensity maps to provide an output indicating said amplitude andphase of said modified wavefront; and a wavefront reconstructor,operative to obtain an output indicating said amplitude and phase ofsaid wavefront being analyzed by reintroducing said estimated knowndifferences from said planar-like wavefront to said output indicatingsaid amplitude and phase of said modified wavefront.
 72. A systemaccording to claim 71 and wherein: said wavefront being analyzed isapproximately a spherical wavefront; and said optical element is a lensoperative to remove the spherical components of said wavefront beinganalyzed.
 73. A system according to claim 71 and wherein: said wavefrontbeing analyzed is a tilted wavefront with additional features; and saidoptical element is a prism operative to remove the tilt component ofsaid wavefront being analyzed.
 74. A method of wavefront analysiscomprising: obtaining a plurality of differently phase changedtransformed wavefronts corresponding to a wavefront being analyzed whichhas a polarization; obtaining a plurality of intensity maps of saidplurality of phase changed transformed wavefronts; and employing saidplurality of intensity maps to obtain an output indicating saidpolarization of said wavefront being analyzed.